Syntax:
<object_parameter> month_start
Return:
First day of the month containing the date
<object_parameter>.
Parameter <object_parameter>:
Required parameter; type is date or datetime; parameter name omitted.
Example:
First day of the month containing 1980-02-27.
NLC snippet: 1980-02-27 month_start // result is date 1980-02-01.