Rounding error in datetime conversion

I think I found a slight rounding error in the function absolutedate_to_datetime() (in pyhelpers.py). The error is only of one millisecond but caused some sanity checks in the code I am using to fail, which can be quite annoying.

For instance, when converting 31.526168 seconds to seconds and microseconds, the function returns 31 seconds and 526167 micreseconds (because in Python, 31.526168 - 31 = 31.52616799999… and the function truncates the decimal part instead of rounding it off)

A suggestion would be to replace line 121 of pyhelpers.py :

microseconds = int(1000000.0 * (seconds - math.floor(seconds)))

by something like that :

microseconds = round(1e6*(second - int(second)))

Best regards

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Hello,

The suggestion of the OP introduces a new error if we have (as a float) 999999.5 < microseconds < 1000000 (for example seconds=11.99999967) which will be rounded to 1000000 which is not accepted in a datetime (it requires microseconds < 1000000).

A solution could be to add a second and put microseconds=0 but it will lead to a painful management of cases where seconds = 59 we need to add a minute, if minutes = 59 we need to add an hour, ...

I propose the following: in orekit, seconds are float, so we can keep it as float and pass it to a timedelta object (which accept float seconds) which will do all the painful management

return datetime(or_date.getYear(), or_date.getMonth(), or_date.getDay(), or_time.getHour(), or_time.getMinute()) \ 
     + timedelta(seconds=seconds_float)

and if we want to keep the same leap second management (if >= 60 then 59.999999) we have this just before:

seconds_float = or_time.getSecond()
if seconds_float >= 60:  # leap second
    seconds_float = 59.999999

Note that we can't do min(59.999999, or_time.getSecond() because it will round 59.99999967 to 59.999999 which is incorrect as we are closer to 60.000000 and in this case we should add a minute and have seconds=0.

+1. Thanks.