local-time is a development library for manipulating date and time
 information in a semi-standard manner. It is based almost entirely off of
 Erik Naggum's paper, The Long, Painful History of Time.
 .
 It includes such features as: Time and date arithmetic, ISO 8601 timestring
 formatted output and parsing, Reader macros to embed timestrings directly
 in code, Timezone handling (will read unix tzfile format), Conversion
 between universal and unix time epochs, Julian date calculation.