Add Mabaruma (Guyana) to your list and use my-locations table to visually convert it's time to another timezone or city time.
Mouse over the colored hour-tiles and glance at the hours selected by the column.

Current time zone for Mabaruma (Guyana) is America/Guyana, whose offset is GMT-4 from Greenwich Mean Time (GMT).

The IANA timezone identifier for Mabaruma, Guyana is "America/Guyana"

It currently does not observe Daylight Savings Time.