# UTC timestamp format for launch vehicles

Has anyone ever seen UTC timestamps of the format xxx:HH:mm:ss.sss? What are the three x's at the front. For reference, this timestamp belongs to an upcoming launch in June of 2019.

• I think it would be best if you shared a link to your example, or a screen shot. It doesn't make sense to me. See this answer for example. – uhoh Jun 7 '19 at 20:42
• Upcoming (or perhaps past) launch of what vehicle? A link would be a very good thing. I am downvoting for three reasons. One, I do not like images that do not have an explanatory alt text. It's important to remember that an image is worth a thousand words (of alt text).Two, no link. Three, the very vague "upcoming launch in June of 2019". – David Hammen Jun 8 '19 at 3:44
• @DavidHammen: Even worse, it is an image of text, which is the absolute most worthless kind of image there is. Not only is it completely useless for visually impaired readers, it doesn't even add any additional information for sighted readers. – Jörg W Mittag Jun 8 '19 at 14:59
• Liftoff precisely at midnight (to the millisecond) UTC sounds like a strange coincidence too. Are you sure those are in fact UTC times rather than some sort of mission elapsed timescale? – hmakholm left over Monica Jun 8 '19 at 17:01

## 3 Answers

This is the n-th day of the year, going from 1 to 365 (or 366).

So 006 would be January 6.

• That was my first thought as well. The launch this is scheduled for is in June though and this prediction was made in March. I edited the question to add that. – Knudsen Number Jun 7 '19 at 19:26
• There was no launch on 2019 January 6. The first launch in 2019 was on January 10. – David Hammen Jun 8 '19 at 3:50
• It would be nice to know where the timestamp comes from. Could be a format error and displaying the month (June -> 6) instead of the day. – Floern Jun 8 '19 at 8:17
• But in the question the timestamp 006 belonged to June 2019 . – Uwe Jun 10 '19 at 15:23

To confirm other answers that the leading three-digit number is day number for the year starting with 1 being 01-Jan:

Note the counter in the lower-left of the video [ISS] Launch of Antares Rocket with Cygnus CRS-2 Spacecraft to ISS is 194 16:52:14.xxx at launch, corresponding to a 13 July 2014, 16:52:14 launch time, with 13-July-2014 being the 194th day of 2014

If you are seeing a three digit 006 immediately before hours for a launch in June, then something is strange.

days:hours:minutes:seconds.fractions_of_seconds