TIME_SLICE

TIME_SLICE(date_or_time_expr, slice_length, unit[, start_or_end])

Calculates one of the endpoints of a "slice" of time containing the date specified by date_or_time_expr where each slice has length of time corresponding to slice_length times the date/time unit specified by unit. The slice start/ends are always aligned to the unix epoch 1970-01-1 (at midnight). The fourth argument specifies whether to return the begining or the end of the slice ('START' for begining, 'END' for end), where the default is 'START'.

For example, TIME_SLICE(T, 3, 'YEAR') would return the timestamp corresponding to the begining of the first 3-year window (aligned with 1970) that contains timestamp T. So T = 1995-7-4 12:30:00 would output 1994-1-1 for 'START' or 1997-1-1 for 'END'.