Never knew about the "cal" command. I especially like that you can quickly look up a previous or future month/year.
>> cal 3 1973
quickly shows a calendar of March 1973
The "+n" syntax is not standards compliant, from the tail info page (on fedora 19):
On older systems, the leading '-' can be replaced by '+' in the obsolete option syntax with the same meaning as in counts, and obsolete usage overrides normal usage when the two conflict. This obsolete behavior can be enabled or disabled with the '_POSIX2_VERSION' environment variable (*note Standards conformance::).