This public dataset is Monthly(GMT):

 Accumulation during 00:00:00 of the first day of the month and 23:59:59 of the end day of the month.
(In case of the beginning or the end of the data, accumulation starts from the beginning of the data, or ends up to the end of the data.)

How to use:

 Please select station from map, then it displays rain gauge data to graph.