Jinja2 filter that formats a date and optionally localizes it to client timezone

jinja2_dateformat.py

from dateutil import tz
from jinja2 import Undefined

client_timezone = tz.gettz('PST8PDT') # timezone to translate to

@app.template_filter()
def dateformat(value, format=None, rebase=True):
    if value is None or isinstance(value, Undefined):
        return ''

    if value.year < 1900:
        return '' # prevent strftime() errors
    
    localize = lambda v: (makeAware(v).astimezone(client_timezone) if (v and rebase) else v)
    formatters = {
        datetime.datetime: ('%m/%d/%y %r', lambda v: localize(v)),
        datetime.date:     ('%m/%d/%y',    lambda v: localize(datetime.datetime.combine(v, datetime.time(0, 0, 0)))),
        datetime.time:     ('%r',          lambda v: localize(datetime.datetime.combine(datetime.datetime.now(), v)))
    }
    
    for t, formatter in formatters.items():
        if value.__class__ == t:
            defaultFormat, localizeVal = formatter
            return localizeVal(value).strftime(format or defaultFormat)
    
    # Unknown type
    raise ValueError('value must be a datetime, date, or time')