Prints a month's calendar. If width is provided, it specifies
the width of the columns that the numbers are centered in. If
length is given, it specifies the number of lines that each
week will use.
An unrelated but handy function that takes a time tuple such are
returned by the gmtime() function in the time
module, and returns the corresponding Unix timestamp value, assuming
an epoch of 1970, and the POSIX encoding. In fact,
gmtime() and timegm() are each others inverse.