Hi, Another useful source for historical time zone information appears to be a series of circulars with the title "Standard Time Throughout the World" issued between 1925 and 1950 by the U.S. Bureau of Standards. I found the following issues online: Circular 280 (1925) https://nvlpubs.nist.gov/nistpubs/Legacy/circ/nbscircular280.pdf https://catalog.hathitrust.org/Record/007291123 Circular 399 (1932) https://nvlpubs.nist.gov/nistpubs/Legacy/circ/nbscircular399.pdf https://catalog.hathitrust.org/Record/007290917 Circular 406 (1935) https://nvlpubs.nist.gov/nistpubs/Legacy/circ/nbscircular406.pdf https://catalog.hathitrust.org/Record/007290977 Circular 496 (1950) https://nvlpubs.nist.gov/nistpubs/Legacy/circ/nbscircular496.pdf https://catalog.hathitrust.org/Record/007290970 Rob van Gent