(new Date('1906-12-31')).getTime()
=-1988236800000
(new Date('1907-01-01')).getTime()
=-1861920000000
(new Date('1910-12-31')).getTime()
=-1862006400000
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
One more example: