Mathematica has a highly flexible system for handling dates and times in almost any format, automatically converting between formats, and when necessary parsing strings representing dates.
DateString — current or specified date as a string in many possible formats
$DateStringFormat — default date string format
$TimeZone — resettable current time zone
DateList — date elements as numbers in
{y, m, d, h, m, s} format
Clock — real-time dynamic clock variable
DatePlus — add or subtract days, weeks, etc. to a date list or string
DateDifference — find the difference in days, weeks, etc. between two dates
DateListPlot — plot data associated with dates specified in any format
DatePattern — date pattern for string manipulation
