On Fri, 21 Aug 2020 at 06:02, griffin tucker <xfssxsltislti2490@xxxxxxxxxxxxxxxxxxx> wrote: > > thanks for taking the time to respond to my seemingly stupid questions. > > what about interplanetary timestamps? and during transit to the > moon/planets when time slows? A little bit of searching provides the answers to your questions, which are heading off topic. 1. SR and GR time dilation effects are very small [1]. (~0.000027 seconds per day on the ISS [2][3]). 2. It's probably UTC everywhere in the solar system by definition. (Fixed offset for longitudinal distribution on the surface of a spinning planet is a separate issue [4]. It's UTC on the ISS [5] and apparently NASA probes too [6]). 3. Unix time (time_t) works in UTC but with leap seconds ignored [7], so is not appropriate for anything important in space. (Imagine if every time a leap second was added GPS was off by most of the distance to the moon)! [1] https://en.wikipedia.org/wiki/Time_dilation#Combined_effect_of_velocity_and_gravitational_time_dilation [2] https://www.businessinsider.com/do-astronauts-age-slower-than-people-on-earth-2015-8?r=US&IR=T [3] https://spaceflight.nasa.gov/station/crew/exp7/luletters/lu_letter13.html [4] https://en.wikipedia.org/wiki/Time_zone [5] https://en.wikipedia.org/wiki/International_Space_Station#Crew_activities [6] https://solarsystem.nasa.gov/basics/chapter2-3/ [7] https://en.wikipedia.org/wiki/Unix_time
