DateAdd

Adds a specified amount of time to a date.

Signature

DateAdd(string date, number amount, string unit)

Parameters

• date (string): The base date string.
• amount (number): The integer amount to add. Negative values subtract.
• unit (string): The time unit. Case-insensitive.

Returns

• string: The modified date in ISO 8601 format (yyyy-MM-ddTHH:mm:ss.fffZ).

Description

Parses the date, adds the specified amount, and returns the result. Valid units (singular or plural):

Unit	Effect
day / days	Adds calendar days
week / weeks	Adds weeks (7 days per week)
month / months	Adds calendar months
year / years	Adds calendar years
hour / hours	Adds hours
minute / minutes	Adds minutes
second / seconds	Adds seconds

Throws a runtime error if:

• The date string is invalid.
• The amount is not an integer.
• The unit is not recognised.

Examples

var tomorrow = DateAdd("2025-10-31", 1, "day")
# tomorrow = "2025-11-01T00:00:00.000Z"

var lastWeek = DateAdd("2025-10-31", -1, "week")
# lastWeek = "2025-10-24T00:00:00.000Z"

var nextMonth = DateAdd("2025-10-31", 1, "month")
# nextMonth = "2025-11-30T00:00:00.000Z"

var inTwoHours = DateAdd("2025-10-31T14:00:00.000Z", 2, "hours")
# inTwoHours = "2025-10-31T16:00:00.000Z"