Fix printing the last day in a 400 year cycle.

[BillyONeal]

This was reported to me by "Jag S" over email trying to print 2000-12-31. The cause appears very similar to https://github.com/microsoft/cpprestsdk/pull/1550/files/198b034679cf7f962e242977b99ea5c63ad9eb03

I think this will cause a denial of service bug similar to the last day 365 one in the year 2400.

[baptistemcn]

Member of the team of "Jag S" here, Thank you very much !