Take the 2-minute tour ×
English Language & Usage Stack Exchange is a question and answer site for linguists, etymologists, and serious English language enthusiasts. It's 100% free, no registration required.

What is the difference with using PT (Pacific Time) vs PDT (Pacific Daylight Time) or PST (Pacific Standard Time)? When you write the time, 2:00pm PT, would that be considered incorrect because it is not specific enough?

share|improve this question
1  
Please try to avoid these abbreviations if any part of your audience lives outside of North America. –  user16269 Oct 30 '12 at 6:52

3 Answers 3

My understanding, and the way things are typically named at least in the context of computing (I'm a programmer by trade), has always been the following:

  • PDT = Pacific Daylight Time = fixed to UTC-7
  • PST = Pacific Standard Time = fixed to UTC-8
  • PT = Pacific Time = a general reference to the time zone, which alternates between PDT and PST depending on the time of year.

Colloquially, people seem to like using PST and PT interchangeably, and will still (IMO, incorrectly) refer to times as PST even when daylight savings time is in effect and Pacific Time is UTC-7.

Also, colloquially, I have seen PDST sometimes used interchangeably with PT to refer to the timezone that alternates between PDT and PST.

This is all oversimplified, as daylight savings rules are different in different cities and countries. With that in mind, another way of viewing it is:

  • PDT: A fixed, standard time, always UTC-7.
  • PST: A fixed, standard time, always UTC-8.
  • PT (or rarely, PDST): A vaguer concept taken to mean "whatever UTC offset is currently in effect in the Pacific Timezone, in the location given by context".

Usually, then, when talking to humans (as opposed to computers) you'd use PT (or, colloquially, PST, even though it's arguably incorrect) to mean "whatever time it is in Pacific Time in whatever location we're talking about".

So:

"I'll meet you in San Francisco Nov 1st, 5:00 PM PT" means "on November 1st, when clocks in San Francisco say 5:00 PM", which in that case would specifically be 5:00 PM PDT (UTC-7).

Likewise, "I'll meet you in San Francisco Nov 3rd, 5:00 PM PT" means "on November 3rd, when clocks in San Francisco say 5:00 PM", which in that case would be 5:00 PM PST (UTC-8).

Mountain Time, for example, is slightly more complicated than Pacific Time because it covers a larger area with more diverse daylight savings rules (e.g. much of Arizona does not observe daylight savings time).

In computing we tend to just represent times in UTC to avoid ambiguity.

Talking to a human you'll be fine saying "Pacific Time", "PT", or "PST" (which, again, has come to be interchangeable with "PT" although purists like myself believe otherwise :) ). If somebody says "PST" to you, 99% of the time they just mean "Pacific Time" in general as per current daylight savings time rules.

I believe the use of "PST" to mean "Pacific Time" has become so common in language that it's pretty much "official".

share|improve this answer

In most cases, PT is specific enough. The only exceptions would be on the day the clocks change. Also, in common speech, people often use PST when they mean PT.

share|improve this answer
    
On any given day, many folks will have trouble remembering if they are on PST or PDT. You can get around that by saying PT, which means 2PM in the Pacific time zone, irrespective of whether or not the zone is in Daylight or Standard time. So, I agree with Charles - not only does PT suffice, it might also be less confusing. –  J.R. Oct 29 '12 at 19:07
    
I always forget that as well, which is why I tend to use PT. I'd rather write PT instead of getting PDT and PST mixed up. –  Sandro Oct 29 '12 at 19:27

According to the Time Zone Abbreviation chart on www.timeanddate.com, both Pacific Standard Time and Eastern Standard Time show an acceptable alternate abbreviation of "PT" or "ET" instead of the primary abbreviation of "PST" or "EST". (Central Time does not have a simpler version - "CST" and "CDT" are listed as the official abbreviations.)

Time and Date Abbreviation Chart

share|improve this answer
    
+1 The Abbreviation chart at timeanddate.com/library/abbreviations/timezones is frightening... CST can mean China Standard Time (UTC+8), Central Standard Time (UTC-6), or Cuba Standard Time (UTC-5). –  rajah9 Oct 30 '13 at 19:34

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.