py-time-lib

This is a time library for python that attempts to handle some of the complexities associated with time.

Features:

• Leap second support
• Support for dates arbitrarily far into the past or future (taking advantage of the unlimited size of python ints)
• Limited timezone support (only counting current rules, not past rules)
• Approximate support for other time scales:
  • TAI: International Atomic Time
  • TT: Terrestrial Time
  • TCG: Geocentric Coordinate Time
  • TCB: Barycentric Coordinate Time (probably inaccurate)
  • TDB: Barycentric Dynamical Time (probably inaccurate)
  • Galactic Coordinate Time (super approximate)
  • Universe Coordinate Time (super approximate)

Examples

Dates:

>>> from py_time_lib import *

# Simple subtraction:
>>> GregorianDate(2024, 4, 26) - GregorianDate(2023, 12, 30)
DateDelta(118)

# Far dates:
>>> GregorianDate(2024, 4, 26) + DateDelta(10 ** 21)
GregorianDate(year = 2737907006988509659, month = 8, day = 28)

# Conversion between date formats:
>>> JulianDate(GregorianDate(2024, 4, 26))
JulianDate(year = 2024, month = 4, day = 13)

>>> IsoWeekDate(GregorianDate(2024, 4, 26))
IsoWeekDate(year = 2024, week = 17, day = 5)

Leap Seconds:

>>> from py_time_lib import *

>>> t1 = TimeInstant.from_date_tuple_utc(
  year=2024, month=4, day=26,
  hour=13, minute=2, second=0,
  frac_second=FixedPrec('0.01')
)

# Internally stored as seconds since Jan 1, 1 BCE, Proleptic Gregorian Calendar:
>>> t1
TimeInstant(FixedPrec('63881355757.01'))

# Can handle dates in TAI or UTC format:
>>> t1.to_date_tuple_tai()
DateTupleBasic(
  year=2024, month=4, day=26,
  hour=13, minute=2, second=37,
  frac_second=FixedPrec('0.01')
)

>>> t1.to_date_tuple_utc()
DateTupleBasic(
  year=2024, month=4, day=26,
  hour=13, minute=2, second=0,
  frac_second=FixedPrec('0.01')
)

# T2 is right before the leap second at the end of 2016-12-31:
>>> t2 = TimeInstant.from_date_tuple_utc(
  year=2016, month=12, day=31,
  hour=23, minute=59, second=59,
  frac_second=0
)

>>> t2.to_date_tuple_utc()
DateTupleBasic(
  year=2016, month=12, day=31,
  hour=23, minute=59, second=59,
  frac_second=FixedPrec(0)
)

# One second later, UTC shows the 61st second of the minute:
>>> (t2 + TimeDelta(1)).to_date_tuple_utc()
DateTupleBasic(
  year=2016, month=12, day=31,
  hour=23, minute=59, second=60,
  frac_second=FixedPrec(0)
)

# Two seconds later, 2017 starts normally:
>>> (t2 + TimeDelta(2)).to_date_tuple_utc()
DateTupleBasic(
  year=2017, month=1, day=1,
  hour=0, minute=0, second=0,
  frac_second=FixedPrec(0)
)

Time Zones:

>>> from py_time_lib import *

>>> chicago = TIMEZONES['proleptic_variable']['America/Chicago']

>>> t1 = TimeInstant.from_date_tuple_utc(
  year=2024, month=4, day=26,
  hour=11, minute=2, second=0,
  frac_second=FixedPrec('0.01')
)

>>> t1.to_date_tuple_utc()
DateTupleBasic(
  year=2024, month=4, day=26,
  hour=11, minute=2, second=0,
  frac_second=FixedPrec('0.01')
)

# In April, Chicago is 5 hours behind UTC:
>>> t1.to_date_tuple_tz(chicago)
DateTupleTZ(
  year=2024, month=4, day=26,
  hour=6, minute=2, second=0,
  frac_second=FixedPrec('0.01'),
  dst_second_fold=False
)

Time Scales:

>>> from py_time_lib import *

>>> t1 = TimeInstant.from_date_tuple_utc(
  year=2010, month=1, day=1,
  hour=0, minute=0, second=0,
  frac_second=0
)

>>> t2 = TimeInstant.from_date_tuple_utc(
  year=2024, month=1, day=1,
  hour=0, minute=0, second=0,
  frac_second=0
)

# In 2010, TCB is approximately 48.3 seconds ahead of TAI:
>>> t1.get_mono_tai_offset(TimeInstant.TIME_SCALES.TCB)
FixedPrec('48.3307954016341152648')

# In 2024, TCB is approximately 55.2 seconds ahead of TAI:
>>> t2.get_mono_tai_offset(TimeInstant.TIME_SCALES.TCB)
FixedPrec('55.1804027969721473364')