Script Writing - Working With Calendars

Overview

The Calendar class is used to manipulate dates such as adding or subtracting days, months, or years from a given date. Calendar is more flexible than the simpler Date object for doing things like 

• Adding X number of days to a date
• Finding the first or last day of the month
• Setting specific components of a date (like the hour or minute used with Date & Time fields)

Also, the Calendar class can be used to create date variables to be referenced in your script. 

📅 Common Calendar Fields

📅 Common Calendar Methods Used to Add or Subtract

Examples 

The two examples below show how to use a Calendar object to add 3 days to the current date, and how to subtract 3 day from the current date. 

//EXAMPLE 1 - Set a Task Due Date field's Value to be 3 Days After The Current Date
//get the current date
def cal = Calendar. getInstance()

//Add 3 days to the current date
cal.add(Calendar.DAY_OF_MONTH, 3)

//get the new Date object
def dueDate = cal.getTime()

//assign the dueDate to the taskEndDate field
currentValues["taskEndDate"] = dueDate


//EXAMPLE 2 - Same as EXAMPLE 1 above, but showing how to SUBTRACT 3 Days from the Current Date instead of ADDING 3 Days
//get the current date
def cal = Calendar. getInstance()

//Add 3 days to the current date
cal.add(Calendar.DAY_OF_MONTH, -3)

//get the new Date object
def dueDate = cal.getTime()

//assign the dueDate to the taskEndDate field
currentValues["taskEndDate"] = dueDate

The example below shows how use a calendar object to set a date field's value to the first day of the month following the initial date entry.

//Create date variable
Date theDate = currentValues["taskEndDate"] as Date

//Create calendar variable for date manipulation
Calendar calendar = Calendar.getInstance()

//Set calendar date to date variable
calendar.setTime(theDate)

//Add one month to date
calendar.add(Calendar.MONTH, 1)

//Set calendar date to the first day of the month
calendar.set(Calendar.DAY_OF_MONTH, calendar.getActualMinimum(Calendar.DAY_OF_MONTH))

//Set date variable equal to the calendar variable
theDate = calendar.getTime()

//Set date field to the new date
currentValues["taskEndDate"] = theDate

Related Articles: 

• Script Writing - Using Variables
• Script Writing - Using Functions
• App Script Best Practices
• App Script Example Library