http_date.py

import datetime

def http_date(dt=None):
    """Return an RFC 7231 HTTP date formatted string

    Input may be an epoch timestamp, or datetime object.
    If a naive datetime object, it must be in GMT already.
    If not specified, now is assumed.
    """
    if dt is None:
        dt = datetime.datetime.utcnow()
    if isinstance(dt, (int, float)):
        dt = datetime.datetime.utcfromtimestamp(dt)
    if dt.tzinfo is not None:
        dt = dt.astimezone(datetime.timezone.utc).replace(tzinfo=None)

    weekday = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"][dt.weekday()]
    month = [
        "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct",
        "Nov", "Dec"
    ][dt.month - 1]

    return "{}, {:02d} {} {:04d} {:02d}:{:02d}:{:02d} GMT".format(
        weekday, dt.day, month, dt.year, dt.hour, dt.minute, dt.second
    )