Each field of a date expression is a date unit. A date unit contains a value and a time type as follows:
time_type:value
Time types are:
YEAR (year)
MONTH (month)
DAY (day)
HOUR (hour)
MIN (minute)
SEC (second)
The following code examples are valid date unit expressions (as well as date expressions):
YEAR:1998
MONTH:event1.someattr
Note: When using constant numbers to specify the value of a time unit, the "0" digit should not appear at the beginning. For example, write March as MONTH:3, not as MONTH:03.
