UTC+00:20 is an identifier for a time offset from UTC of +00:20.
UTC+00:20 was used in the Netherlands from 1 May 1909 to 16 May 1940. It was known as Amsterdam Time or Dutch Time.
The exact timezone was GMT +0h 19m 32.13s until July 1, 1937, when it was simplified to GMT +0h 20m. When Germany occupied the Netherlands in World War II, Berlin Time was adopted, and this has been retained ever since.
The reason for the specific offset of +0h 19m 32.13 was that the timezone was centered on the mean solar time of the Westertoren (4°53'01.95" E Latitude), the tower of the Westerkerk church in Amsterdam.