Real Answers from Real Pilots

Coordinated Universal Time

I’m a little surprised no one’s asked this yet at least to my knowledge on the forum.

I just got a flight simulator app for my i-phone, it’s really good, you can change the time of day and everything, but when you do that, you have to set it by UTC time instead of standard.

Supposedly this is the standard used in aviation. This is nothing like military time as I hoped, the app doesn’t explain how it works, it only gives an example: if you want the sim session set to noon in San Fransisco, that would be about 20h on the UTC clock. Can someone please explain how UTC time really works in detail?

UTC time, also known as Zulu time (which used to be known as Greenwich Mean Time “GMT”), is the universally accepted time format and the actual time in Greenwich England. UTC or Zulu time has no time zones, to convert to UTC you add or subtract some amount from your local time zone and to convert to local is the opposite. Example: I live in California, it is currently 09:09UTC/Zulu and 01:09 Pacific Standard Time, no matter what time of day it is I would add +8 to my local to get UTC or -8 from UTC to get local time… During daylight savings time it is +/-7 hours here in California. It is +/-5 hours for Eastern Standard Time, and +/-4 during daylight savings on the east coast.

It all starts to make sense once you start using it, but hopefully that helps.


UTC (aka Zulu aka GMT) is Coordinated Universal Time which is exactly what it is. As I trust you’re aware there are time zones around the world which can make things somewhat confusing. If your flight departs JFK at 0600 (EST) that’s 0700 (CST) in ORD or 0800 (MST) in DEN or 0900 (PST) in LAX which can be confusing when trying to COORDINATE flights (and that’s just in the US!). By using UTC we’re ALL on the same clock and it’s 1100Z EVERYWHERE. Which is One more reason to love Hawaii, we don’t change our clocks throughout the year (no daylight savings nonsense) so it’s ALWAYS +10 hrs for Zulu.


I have to ask, how does a flight simulator app for the iPhone work? It seems like such a small device to use for such program.

I have the same app I play around with on my IPad and it is a lot of fun! :slight_smile: some of the in app purchases are worth it, just sayin!

No there’s no separate midwest time, to keep all the different zones lined up they are based on whatever time zone you are in, if you’re eastern then it’s +/- 4-5 depending on daylight or standard time. I did one day look, and in the “world clock” page in the clock on an iPhone you can add UTC as a zone, if you happen to be an iPhone user.