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Refine documentation of epoch & full_year

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This commit is contained in:
Jeff Epler 2025-05-21 10:21:57 +02:00
parent 4e3e36b53d
commit 2677ea2df2
1 changed files with 10 additions and 1 deletions
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11
src/wwvb/__init__.py
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@ -375,6 +375,9 @@ class WWVBMinute(_WWVBMinute):
"""
epoch: int = 1970
"""The full (4-digit) year of the start of the WWVB epoch
See `full_year` for documentation of how this class property is used."""
def __new__( # noqa: PYI034
cls,
@ -414,13 +417,19 @@ class WWVBMinute(_WWVBMinute):
def full_year(cls, year: int) -> int:
"""Convert a (possibly two-digit) year to a full year.
If the argument is above 100, it is assumed to be a full year.
If the argument is at least 100, it is assumed to be a full year.
Otherwise, the intuitive method is followed: Say the epoch is 1970,
then 70..99 means 1970..99 and 00..69 means 2000..2069.
To actually use a different epoch, derive a class from WWVBMinute (or
WWVBMinuteIERS) and give it a different epoch property. Then, create
instances of that class instead of WWVBMinute.
Unfortunately, even by setting ``epoch = 0`` in a subclass it is not possible
to generate timecodes for AD 1..99. This is because the definition of the phase
modulation signal refers to the "minute of the century", where a century starts
in year "xx00". Computing this requires constructing ``datetime(0,1,1)`` which is
not permitted.
"""
century = cls.epoch // 100 * 100
if year < (cls.epoch % 100):