none_if_epoch.py

from django import template
from django.utils.timezone import utc
import datetime

register = template.Library()


@register.filter
def none_if_epoch(value):
    epoch = datetime.datetime(1970, 1, 1, tzinfo=utc)
    if value == epoch:
        return None
    else:
        return value


@register.filter
def is_epoch(value):
    if value is None:
        return True
    epoch = datetime.datetime(1970, 1, 1, tzinfo=utc)
    return value == epoch