The python dateutil module provides powerful extensions to the standard
datetime module.

* Computing of relative deltas (next month, next year, next monday,
last week of month, etc.)

* Computing of relative deltas between two given dates and/or
datetime objects

* Computing of dates based on very flexible recurrence rules, using
a superset of the iCalendar specification. Parsing of RFC strings
is supported as well.

* Generic parsing of dates in almost any string format.

* Timezone (tzinfo) implementations for tzfile(5) format files
(/etc/localtime, /usr/share/zoneinfo, etc.), TZ environment
string (in all known formats), iCalendar format files, given
ranges (with help from relative deltas), local machine timezone,
fixed offset timezone, UTC timezone, and Windows registry-based
time zones.

* Internal up-to-date world timezone information based on Olson's
database.

* Computing of Easter Sunday dates for any given year, using Western,
Orthodox or Julian algorithms.