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?
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:
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:
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".
"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".
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.)
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.
To avoid ambiguity or confusion it's best to follow established practice when specifying a time. "PT" refers not to a time, but to a time zone, and can therefore be used (implicitly and unambiguously) to refer to the current time in the Pacific time zone.
If you specify a time (rather than a time zone), you should use the correct one (PDT or PST). Using PST to mean "the current time in the Pacific zone" is wrong (since it not only conflates a time zone with a time, but also implicitly makes "PDT" and "PST" synonyms for nearly half of the year).