pythondatetimegpsleap-second

How to get leap seconds from gps epoch for current date in python

As I understand for now in python there is no function to get leap seconds from gps epoch for current date. The appropriate patch under investigation/development: leap seconds path in datetime

Could you advice the best way how to get leap seconds? I found that solution:

def getLeapSec(Tgps):
  daysFromGPSEpoch = timedelta(seconds=Tgps).days
  tableLeapSec = ([
    [0,  542,  907, 1272, 2003, 2917, 3648, 4013, 4560, 4925, 5290, 5839, 6386, 6935, 9492, 10588, 11865, 12960],
    [0,    1,    2,    3,    4,    5,    6,    7,    8,    9,   10,   11,   12,   13,   14,    15,    16,    17]
                 ])

  for i in range(1, len(tableLeapSec[0])):
    if daysFromGPSEpoch < tableLeapSec[0][i]:
      return tableLeapSec[1][i-1]

Example:

In [25]: Tgps = 1092121243.0

In [26]: getLeapSec(Tgps)
Out[26]: 16
Solution

  • You could use leapseconds module if you have access to the up-to-date tzfile on your system:

    >>> from datetime import datetime, timedelta
>>> import leapseconds
>>> Tgps = 1092121243.0
>>> gps_time = datetime(1980, 1, 6) + timedelta(seconds=Tgps)
>>> leapseconds.dTAI_UTC_from_tai(leapseconds.gps_to_tai(gps_time))
datetime.timedelta(0, 35)

    The main advantage is that tzdata package is updated several times per year by the system automatically (more often than leap seconds are introduced). Your code will use the new data without the need to change it.

    Otherwise, as a fallback, you could hardcode the result of the leapseconds.leapseconds() call:

    >>> import leapseconds
>>> leapseconds.leapseconds()
[LeapSecond(utc=datetime.datetime(1972, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 10)),
 LeapSecond(utc=datetime.datetime(1972, 7, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 11)),
 LeapSecond(utc=datetime.datetime(1973, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 12)),
 LeapSecond(utc=datetime.datetime(1974, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 13)),
 LeapSecond(utc=datetime.datetime(1975, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 14)),
 LeapSecond(utc=datetime.datetime(1976, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 15)),
 LeapSecond(utc=datetime.datetime(1977, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 16)),
 LeapSecond(utc=datetime.datetime(1978, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 17)),
 LeapSecond(utc=datetime.datetime(1979, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 18)),
 LeapSecond(utc=datetime.datetime(1980, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 19)),
 LeapSecond(utc=datetime.datetime(1981, 7, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 20)),
 LeapSecond(utc=datetime.datetime(1982, 7, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 21)),
 LeapSecond(utc=datetime.datetime(1983, 7, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 22)),
 LeapSecond(utc=datetime.datetime(1985, 7, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 23)),
 LeapSecond(utc=datetime.datetime(1988, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 24)),
 LeapSecond(utc=datetime.datetime(1990, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 25)),
 LeapSecond(utc=datetime.datetime(1991, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 26)),
 LeapSecond(utc=datetime.datetime(1992, 7, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 27)),
 LeapSecond(utc=datetime.datetime(1993, 7, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 28)),
 LeapSecond(utc=datetime.datetime(1994, 7, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 29)),
 LeapSecond(utc=datetime.datetime(1996, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 30)),
 LeapSecond(utc=datetime.datetime(1997, 7, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 31)),
 LeapSecond(utc=datetime.datetime(1999, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 32)),
 LeapSecond(utc=datetime.datetime(2006, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 33)),
 LeapSecond(utc=datetime.datetime(2009, 1, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 34)),
 LeapSecond(utc=datetime.datetime(2012, 7, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 35)),
 LeapSecond(utc=datetime.datetime(2015, 7, 1, 0, 0), dTAI_UTC=datetime.timedelta(0, 36))]

    You have to update the list manually when the next leap second is introduced in this case.

    The authoritative source for the leap seconds updates is Bulletin C issued by IERS that also provides TAI-UTC data since 1961.

    You could ping IESR once in a half-year (e.g., January, July), to find out programmatically using leap_second_client.py when the next leap second is scheduled.