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Observation Times Incorrect on Day Before DST Changes

I noticed that some observations I made during Standard Time last year have a time stamp that is one hour late.  I am not sure if it makes any difference but I believe the site I am using with them was created after the DST change.  Details as follows:

1.  I have a session of observations that starts October 31st, 2020 at 9:34:30pm in SkySafari.  The site for this observation is set to -7.0 hours  Standard Time Zone from GMT.

2. These observations start at 8:34:30pm in my astronomy software and they were imported from SkySafari with a download from LiveSky. 

3. If I look at a current download of this observation session.  For the 8:34:30pm / 9:34:30pm observation, the specified Julian / UTC time is 2459154.6489637927,"2020-11-01T03:34:30.471Z".  I have verified the Julian coversion to be correct with a Julian / UTC calculater.

4.  I checked and Daylight Time switched to Daylight Savings time at 2:00am local time in my time zone (US Mountain Time), which would have been 9:00 UTC; so this observation was a few hours before the DST cutover and should not have changed yet.

5.  This appears to be DST related because I have another session on April 4, 2021 with a single observation at the same site.  This was also imported from SkySafari into my astronomy software and the time stamps match.

6. I have another session at the same site the night of 10/30/2020 and those time stamps match.  I think this issue is occuring when the local DST cutover time overlaps with the UTC time for the DST cutover. (ie The day before DST, SkySafari doesn't convert the local time cutover at 2:00am to UTC time which would be 9:00am so it changes the local time for any observations past 8:00pm local Standard Time)


  • 0
    Keiron Smith


    Can you reproduce this issue?  

    You can choose an object, create an observation, set a date in the past similar to the observation that is in question.

    What are the steps to reproduce this issue (with screenshots please).


  • 0
    Bryan Hamilton

    This gets confusing.  I actually now think it's the other software with the problem.  I'll wait to verify this from them before giving any further info.

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