I am archiving and translating postcards sent to my great grandmother Dorothy by her cousin Efim from 1908 to 1910. I noticed a curious thing. The date hand written by Efim on the card sent to Dorothy, is always AFTER the date of the mail service stamp. Was it common for postcards to be pre-paid, stamped with a date and THEN composed to the intended receiver and dated by the author? Or am I missing something? How could a postcard be stamped by the mail service/post office BEFORE it's been written out?
Because Russia had a different calendar.
The modern calendar we use today is the Gregorian calendar. 365 days most years, but with a slightly complex system of leap years that result in an average year length of 365.2425 days, very close to the 365.2422 days of an actual tropical year (the period between equinoxes or solstices). That calendar remains in sync with the seasons over a period of 3000 years (longer than its been in use).
Previously the Julian calendar was used, dating back to Roman times. That calendar has leap years every 4 years, period, so averages 365.25 days per year, a discrepancy of 1/128th of a day per year. That's not a lot, but over hundreds of years, it does add up. And with a longer year length the result is that Julian calendar dates end up earlier than Gregorian calendar dates.
Most of Europe switched to the Gregorian calendar in the 18th century, except for big chunks of Eastern Europe that were predominantly Eastern Orthodox, including Russia. This didn't change until after the revolution in 1918.
So, the dates on the cards sent from Germany and Switzerland were using the Gregorian calendar, while the postal stamps from Russia would have used the Julian calendar (which ran about 14 days earlier).