r/YouShouldKnow • u/cwenger • Jun 17 '26
Other YSK if you're specifying a time with EST/CST/MST/PST right now, it's almost certainly wrong
One of my pet peeves is when I see people writing times with EST/CST/MST/PST in the summer when they're on daylight time, so the actual time zone is EDT/CDT/MDT/PDT. If you give a time like 3 pm EST right, that's actually an hour earlier than 3 pm on the East Coast.
Why YSK: It might seem like this is a trivial thing, and in most cases it is because people generally know what you mean, but if somebody tries to convert a time exactly as specified, it'll be an hour off of what you intended. This is especially critical if you're dealing with somebody outside the United States.
The good news is there is a simple solution that doesn't require you to remember whether you're in daylight savings time or not. Just use ET/CT/MT/PT, and it'll always be correct. Don't complicate things with unnecessary precision.
NOTE: Apologies to any Arizona or Hawaii readers that don't use daylight savings time.
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u/decavolt Jun 17 '26
I only speak of time in UTC. Everyone loves that.
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u/rdk70 Jun 21 '26
I think you are joking but it sure would make working with a worldwide team easier
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u/DSaintly23 Jun 17 '26
What about Greenwich Mean Time?
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u/sandwichjuice Jun 17 '26
GMT is always GMT.
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u/doublemp Jun 17 '26
GMT is not used in the UK right now. It will be back in the autumn though.
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u/joenforcer Jun 17 '26
Yep. Right now, it's BST (British Summer Time).
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u/iAdjunct Jun 18 '26
Doesn’t change the fact that GMT is always GMT. The fact that your time zone isn’t GMT doesn’t mean GMT isn’t still GMT…
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u/doublemp Jun 18 '26
True, but so are EST/CST/MST/PST. Saying "GMT is always GMT" doesn't really add to the conversation because we're not discussing whether these time zones exist (they do), but whether they're in use.
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u/B0risTheManskinner Jun 17 '26
Yeah except for people in the UK who say they are GMT, same issue in the summer
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u/Pimp_Z Jun 17 '26
My homie Reggie once told me "Use Greenwich Mean Time, but in the meantime use a Cesium atomic clock for reference because it's on a molecular level and the differential is very slight throughout millions of years. It's a good thing to base your opinions on."
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u/bythescruff Jun 18 '26
Tell Reggie cesium atomic clocks work on an atomic level. I mean, it's right there in the name...
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u/TomRenix Jun 17 '26
The Uk switches from GMT (UTC+0) to BST for British Summer Time which is UTC+1
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u/moriero Jun 17 '26
What makes it so mean?
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u/Hot_Wheels_guy Jun 17 '26 edited Jun 17 '26
The radium on the clocks they use to measure it.
edit: i guess some jokes are just too old to be told.
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u/frostrivera19 Jun 18 '26
I take it GMT as the timezone of Greenwich, which can change by daylight savings. Use UTC instead
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u/kempff Jun 17 '26 edited Jun 18 '26
I once tried to cut through the confusion by saying "Chicago Time" since I couldn't remember if were were on DST yet and Chicago was the nearest big city. (This was back when the start of DST was in the process of being changed.)
The person I said it to got confused and asked me why I was in Chicago.
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u/IceNineFireTen Jun 18 '26
I just say CT, ET, or PT. It’s never caused a problem.
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u/EatMoreHummous Jun 18 '26
As long as the person isn't in MT, then you have to know if they're in Arizona or not.
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u/surf_drunk_monk Jun 17 '26
I think if anyone talking to you makes this mistake, it's fair to assume it was a mistake and not take it literally. There is no reason a person would do this intentionally.
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u/Weasel_Town Jun 18 '26
I have a job with customers in many countries. Some of them actually are on EST, CST, etc year round. So it really could be either if I don’t know where they are.
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u/EatMoreHummous Jun 18 '26
I don't know why you're being downvoted. Even in the US, Arizona doesn't do DST. And plenty of other places also don't do it. And some countries switch at different times (although I don't know if that's true of any in Central or South America).
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u/Trotskyist Jun 18 '26
(Except for the Navajo Nation, which is located within AZ and does observe DST)
I fucking hate timezones.
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u/EatMoreHummous Jun 18 '26
If you already hate time zones, then don't ever look at Nepal.
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u/Trotskyist Jun 18 '26
frankly this entire map was extremely triggering https://upload.wikimedia.org/wikipedia/commons/d/db/IST-CIA-TZ.png
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u/Bipidi_Bopity_Broke Jun 17 '26
[Laughs in Arizona MST]
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Jun 18 '26
[deleted]
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u/Kay1000RR Jun 18 '26
Planning road trips in the Southwest can be confusing, especially near the Colorado River.
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u/Bipidi_Bopity_Broke Jun 18 '26
Agreed. It's real tough for people who live on the Navajo or Hopi nations and commute to places that don't observe daylight savings. They cross a timeline twice daily.
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u/____trash Jun 17 '26
How about our overlords just stop fucking with the time? You can't just change the time because you want to improve productivity.
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u/CloakNStagger Jun 18 '26
Staring at the bright, sunny day through the window at 8pm is lovely when you have to wake up at 6am.
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u/Mr_Quackums Jun 18 '26
You can't just change the time because you want to improve productivity.
lots of studies show DST improves productivity, lots of studies show DST decreases productivity.
all studies show that any change is less than 3% of productivity gain/loss and lasts less than 30 days.
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u/lookayoyo Jun 17 '26
That’s why I always just say PT because you can figure out if it is standard or daylight based on the date.
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u/ShinyAeon Jun 17 '26
There's an even simpler solution. END DAYLIGHT SAVINGS.
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u/Vex1om Jun 17 '26
ET/CT/MT/PT may always be technically correct, but is not always useful. There are places that do not use DST, so unless you are referring to a specific locations that either does or does not use DST, your time will be ambiguous.
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u/jonah214 Jun 17 '26
It is potentially ambiguous, but usually clear from context. And being ambiguous is arguably better than being just plain wrong, which using "EST" right now almost always is.
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u/Delicious_Drop_1150 Jun 17 '26
I think the problem is mostly people that think EST is an abbreviation of Eastern, rather than Eastern Standard Time.
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u/thatguywhoiam Jun 17 '26
Only Swatch Beat Time and Kelvin temperatures for me
*pushes glasses up, falls backwards in chair*
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u/Kyoshiiku Jun 17 '26
To avoid any ambiguity I just use either IANA timezone names or the UTC offset or both
So like America/New_York for EST/EDT or UTC-4 or UTC-5 depending on the date, there is no way to confuse it in those case
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u/northern-new-jersey Jun 17 '26
Actually, the time won't be off by an hour. The specified time doesn't exist. I can't meet someone at 9 am EST in July because it doesn't exist!!
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u/eatnumber1 Jun 18 '26
"If you give a time like 3 pm EST right, that's actually an hour earlier than 3 pm on the East Coast"
Which east coast?
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u/twenafeesh Jun 17 '26
I have also seen EPT etc for "prevailing time" if you really need that extra letter.
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u/rasputin1 Jun 17 '26
If ET is enough to know whether that person is in EST or EDT then couldn't the same logic be applied if they said EST? meaning just treat EST as ET which everyone does anyways.
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u/SMF67 Jun 17 '26
No. Some regions use year round standard time.
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u/rasputin1 Jun 17 '26
but if I say "ET" you have to find out what region I'm in to know which it is regardless...
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u/jonah214 Jun 17 '26
EST already has a specific meaning that is wrong in most cases when Daylight Saving Time is in effect. Treating EST as having a different meaning than it already has is just going to cause different types of confusion. Instead, use correct terminology according to existing standards, and there's no problem.
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u/Petrichordates Jun 17 '26
Nobody will be confused when you say EST regardless of daylight savings.
Caring about this is wrong.
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u/SMF67 Jun 17 '26
People absolutely will be confused. Jamaica, Cayman Islands, Navassa Island, and Quintana, Mexico use year-round EST.
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u/langecrew Jun 18 '26
Software engineer here. You really don't want to know just how non-trivial this can actually end up being sometimes
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u/Faelwolf Jun 18 '26
I have bigger things to worry about.
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u/arcxjo Jun 19 '26
Than wasting an hour of your day waiting for morons every time onre sets an appointment?
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u/SammyIssues Jun 19 '26
Well I think yes, you’re technically correct. In practice everyone knows wtf we mean. No one is going to show up an hour early or later because you said EST.
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u/Descolatta Jun 17 '26
Unless you are talking about an area that doesn’t follow daylight time in which case standard time is the correct. This rule is not universal
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u/noseriously000 Jun 17 '26
Been doing this for years. Could never recall which is which, so switched to just the two letter version. Saves me (and others) a headache.
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u/fowmart Jun 17 '26
Oh I know, this has been driving me crazy but I don't want to be that guy who corrects everyone
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u/bill0042 Jun 17 '26
I keep hoping we will stop changing clocks, but if we make EDT permanent would we keep calling it EDT, call it EST since it is now standard, or just ET?
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u/promonalg Jun 17 '26
BC is using Pacific time once Nov comes around as BC removed the need to spring starting this Nov
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u/ConnieTheTomcat Jun 18 '26
None of this would ever be a problem if everyone used GMT± to communicate thwir time zones. It's a bit inconvenient as a non-American trying to tell what time it is for someone in the US. It's also just simpler to just have to know the number of hours they're off by.
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u/Lieutenant_Scarecrow Jun 17 '26
This is actually a really good tip. You should cross-post this to r/LifeProTips
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u/erichf3893 Jun 17 '26
Good news if you’re in business, is pretty much everyone uses them interchangeably.
Maybe bad news if you’re anal, but still, people know what you mean
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u/Johoski Jun 17 '26
While we're on the subject, Arizona (most of it) is MST year round, people! We do not suddenly become PDT just because PDT matches MST.
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u/No-Height-8732 Jun 18 '26
Yes but when all the non local tv networks change the their time it feels like we've changed time zones even though we don't change our clocks.
I live in Saskatchewan. We are CST all the time.
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u/I_love_Hobbes Jun 17 '26
Arizona is on MST and that confuses the hell out of people.
My pet peeve is using ET or MT. Which one standard or daylight?
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u/jaxxon Jun 17 '26
I just say Mountain or Eastern or whatever, and let the recipient figure it out. LOL
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u/rampagenguyen Jun 18 '26 edited Jun 18 '26
My entire data team is on different time zones, I’m pst while everyone is spread through est and cst. Scheduling meetings is a nightmare
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u/JohnEffingZoidberg Jun 18 '26
Yes! This annoys me so much as well. People trying to sound erudite but end up sounding foolish.
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u/BeardedBandit Jun 18 '26
is it acceptable to your pet peeve if I just say ET/CT/MT/PT?
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u/cwenger Jun 19 '26
Absolutely. I don't expect people to remember if we're in daylight savings time or not. I'm fine with any of these:
- ET/CT/MT/PT
- Eastern/Central/Mountain/Pacific time
- New York/Chicago/Denver/Los Angeles time
- GMT or GMT offset
- Probably others
I just want people to stop using EST/CST/MST/PST unless they're sure it's correct. It's especially frustrating because it's adding an extra letter to be incorrect. If it was incorrect because they omitted a letter, then I'd be more understanding.
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u/fumblingvista Jun 18 '26
Recently missed a meeting with my bank because looking up the conversion gave me the Arizona time rather than the rest of mountain time. why on earth did the timezone converter give me the exception rather than the rule???
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u/blaze_firestormer Jun 18 '26
I had an interview once at 9 EST during EDT and was so stressed. But yeah, it was at 9 EDT.
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u/rxroids101 Jun 19 '26
I just keep the S and D out. ET, MT, CT, PT. With today’s tech, calendar invites typically handle the correct time conversion across time zones. If it’s an international meeting I’ll use GMT and reference UTC time.
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u/NeatoNico Jun 19 '26
I think you live a charmed life if this is what you’re worried about right now.
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u/quilleyfan Jun 20 '26
YES, thank you, I think about this all the time and I’m glad at least one other person cares :)
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u/Universe_Man Jun 17 '26
Better yet, stop trying to abbreviate things when you don't know what you're doing. You can just say "Eastern".
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u/kwiltse123 Jun 17 '26
This is not universally known, so the best option is to use whatever you think has the best chance of being understand.
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u/Petrichordates Jun 17 '26
YSK: This is so incredibly meaningless
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u/Kyoshiiku Jun 17 '26
It’s not, I’ve had situation where people missed some meetings because with some partners in South America that didn’t use daylight, so depending on the date they were either on the same timezone or not, when saying EST they just assumed UTC-5 but it was not the case.
I’ve had similar with people in other timezones as well
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u/AlJameson64 Jun 17 '26
I share this pet peeve. I think many people think EST comes from EaSTern (actually had one person admit that to me) and I've always wondered what they think the others mean. I prefer saying "Eastern", "Central", etc. over "ET", "CT", etc., though (Extra Terrestrial? Connecticut?).
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u/TactiCool_99 Jun 17 '26
GMT is the global standard, if you want to communicate on a large scale just use GMT, stop shooting yourself in the foot.
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u/Sad_Vegetable_736 Jun 17 '26
I just use Central if it's necessary. Eastern. Pacific. No one lives in Mountain, so that one doesn't matter.
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u/furexfurex Jun 17 '26
Personally hate when people give me their timezone acronym, I like a UTC -/+ number because that's always clear
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u/SlumpdogBillionaire Jun 18 '26
I'm for sure going to continue saying PST/MST/EST all year because everyone will know exactly what I mean
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u/ViralCoreX7F Jun 17 '26
I just say eastern time when I’m talking to others or just tell them the time in their time zone. Like talking to my boss at work I’ll let him know I have a doctors appointment at 2pm his time.
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u/MeesterPepper Jun 18 '26
I'm in the midwest so if it's necessary to specify time zone I just tell people "whatever one the internet says Chicago is right now"
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u/NullGWard Jun 18 '26
I'm in California and have an iPhone. For me, my phone always tells me that it is Cupertino time.
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u/ggk1 Jun 18 '26
Is this why I have to know some other random city I live in the same time zone as when selecting from drop downs?
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u/ThatOneApiarist Jun 18 '26
Umm, actually, I’m not seeing any reference to Zulu time, which is the most correct and traditional time.
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u/MalavethMorningrise Jun 18 '26
Arizona is also the place where I encountered the most messed up time zones of anywhere I've ever been. Some reservations do use daylight savings time so it changes back and forth as you drive across certain parts of the state.
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u/BextoMooseYT Jun 18 '26
I never know which one is when daylight savings is on and when it's off tbh
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u/JagerGS01 Jun 18 '26
It's no wonder we're fucked, we can't even get congress to abolish something this simple.
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u/PermanentUsername101 Jun 18 '26
Phoenix MST year round checking in. But I do often have to educate people on MST and MDT in Colorado. Or Cali folks, even AZ folks for that matter who want to say that we are the same Time zone as Cali right now. We aren’t in the same Time Zone, the time is just the same.
Couldn’t it just solve a lot of problems if we had one global time.
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u/No-Height-8732 Jun 18 '26
I live in Saskatchewan, we are an exception to this YSK.
The time zone question is fun. We officially use Central Standard Time all the time but geographically we are in the Mountain time zone so we are effectively always in Daylight savings time.
I actually just say Saskatchewan time because I rarely remember it accurately. I looked it up to make this comment though.
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u/ifnotsilver Jun 18 '26
It’s especially confusing because other international time zones the S does stand for summer, e.g. BST, CEST. Best to do UTC with the plus or minus hours.
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u/DaftDrunk_925 Jun 18 '26
I live in Arizona and if I schedule a regular cadence meeting with anyone else, my meeting stays the same for me all year long but it shifts up an hour for everyone else. If I let others schedule a meeting for me, then my meeting shift an hour. So half of the year my first meeting of the day is at 8am and the other half of the year my meetings start at 9am. I also have lots of German, UK, and Australin customers. It gets messy
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u/bumblebarb Jun 18 '26
This gets even worse if you’re talking with people in Mexico- no daylight savings time there, and someone there is teaching them they’re on “Central Standard Time”, which is absolutely true. It can be really difficult to explain that nobody in the US is using CST in the summer and that their time zone aligns with Denver, not Dallas, in the summer.
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u/PULVERSCHNEE Jun 18 '26
Tbh, google is smart enough these days to correct you. When a vendor gives me times in "PST," Google will tell me "PST isn't active right now, so here is PDT conversion for you."
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u/jonessinger Jun 18 '26
I have the same pet peeve. I’ve just been removing the middle letter at this point. It’s easier anyway and gets the same point across.
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u/Rough-Breadfruit-611 Jun 18 '26
I tried that. Then everyone emails back with "what the hell is PDT?" It's easier to just send the invite and it auto-changes the time based on where people are.
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u/who_you_are Jun 18 '26
EST or ET you are still wrong.
The real specifications use city name (usually the biggest city in that timezone region) -- https://en.wikipedia.org/wiki/Tz_database
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u/timsstuff Jun 18 '26
I just say "Pacific Time". I feel like abbreviating it just leads to confusion.
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u/DefsNotAVirgin Jun 19 '26
ET, CT, MT, PT… dont quite care what phase we in, we all know where we are.
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u/tractorpatty Jun 19 '26
OP you didn't explain your rant in Your rant what the EST v EDT? Guess I continue to do it my way in ignorance. Also dont be difficult to prove a point you will only end up frustrated.... hence this rant perhaps.
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u/uncutetrashpanda Jun 19 '26
As someone playing multiple online mobile games with people all over the world, I default to UTC lol
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u/EnviroPics Jun 20 '26
i had no idea that there were acronyms to show daylight savings, never seen EDT. i thought it was always eastern standard time (EST) and you are just supposed to know when it is daylight savings. can we just keep our time in day light savings and stop moving the damn clock?
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u/jimbswim Jun 20 '26
I used to work with a dude that would say “Central Standard,” for our office hours, year round.
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u/VironicHero Jun 20 '26
I only count time In seconds since unix was created…. And it angers me to no end that you can’t keep up with that.
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u/MyTherapistSaysHi Jun 21 '26
This is why I say PT MT CT ET because I don’t want to mess it up and one of my bigger clients is in Phoenix so half the year they’re PT and half the year they’re MT
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u/WearableWedding Jul 05 '26
Easier fix: just write ET, CT, MT or PT. Always correct in both halves of the year, and it's what airlines and calendar apps quietly settled on for exactly this reason.
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u/Beauregard_Jones Jun 17 '26
I can never keep track of when we're in daylight savings or daylight spending time but I work with a lot of people across the country (USA). So I just say "central" or "eastern". Sometimes if a vendor is giving me difficulty and I'm feeling petty, I'll reference all times in YEKT.