We use the following time representations
- TimeStamp
 - A TimeStamp is a floating point number expressing the time in seconds 
since the Epoch at 1970-01-01.
 
- date(Y,M,D,H,Mn,S,Off,TZ,DST)
 - We call this term a date-time structure. The first 5 fields are 
integers expressing the year, month (1..12), day (1..31), hour (0..23) 
and minute (0..59). The S field holds the seconds as a 
floating point number between 0.0 and 60.0. Off is an integer 
representing the offset relative to UTC in seconds, where positive 
values are west of Greenwich. If converted from local time (see stamp_date_time/3),
TZ holds the name of the local timezone. If the timezone is 
not known, TZ is the atom 
-. DST 
is true if daylight saving time applies to the current 
time, false if daylight saving time is relevant but not 
effective, and - if unknown or the timezone 
has no daylight saving time. 
- date(Y,M,D)
 - Date using the same values as described above. Extracted using
date_time_value/3.
 
- time(H,Mn,S)
 - Time using the same values as described above. Extracted using
date_time_value/3.