YearMonth — GraphQL Custom Scalar

Author – apollographql

Date - 2025-12-04

1Overview

This scalar represents a year and month, without any reference to a time zone.

Using RFC 3339 format, a YearMonth is represented as date-fullyear "-" date-month:

date-fullyear   = 4DIGIT  ; 0000-9999
date-month      = 2DIGIT  ; 01-12

3GraphQL input coercion

The input must be a GraphQL StringValue matching the description above.

All other values must raise an error.

4JSON input coercion

The input must be a JSON string matching the description above.

All other values must raise an error.

5JSON result coercion

The result must be a JSON string matching the description above.

6Examples

Because GraphQL StringValue and JSON string are so similar, the first column in the table below may be understood as either a GraphQL StringValue or a JSON string.

Value Description
1983-10 A valid year and month.

These are invalid examples:

Value Why is it invalid
1983-01-20 Day is not allowed.
1983-00 00 is not a valid month.
10000-10 More than 4 digits for date-fullyear.
52-10 Less than 4 digits for date-fullyear.
YearMonth — GraphQL Custom Scalar
  1. 1Overview
  2. 2Recommended Name
  3. 3GraphQL input coercion
  4. 4JSON input coercion
  5. 5JSON result coercion
  6. 6Examples