Rules for date, time, and timestamp arithmetic

The specific rules governing the use of the addition operator with date and time values follow:

• If one operand is a date, the other operand must be a date duration or a labeled duration of years, months, or days.
• If one operand is a time, the other operand must be a time duration or a labeled duration of hours, minutes, or seconds.
• If one operand is a timestamp, the other operand must be a duration. Any type of duration is valid.

The rules for the use of the subtraction operator on date and time values are not the same as those for addition because a date or time value cannot be subtracted from a duration, and because the operation of subtracting two date and time values is not the same as the operation of subtracting a duration from a date or time value. The specific rules governing the use of the subtraction operator with date and time values follow:

• If the first operand is a date, the second operand must be a date, a date duration, a string representation of a date, or a labeled duration of years, months, or days.
• If the second operand is a date, the first operand must be a date or a string representation of a date.
• If the first operand is a time, the second operand must be a time, a time duration, a string representation of a time, or a labeled duration of hours, minutes, or seconds.
• If the second operand is a time, the first operand must be a time or string representation of a time.
• If the first operand is a timestamp, the second operand must be a timestamp, a string representation of a timestamp, or a duration.
• If the second operand is a timestamp, the first operand must be a timestamp or a string representation of a timestamp.