I downloaded and tested the DS1307 and time libraries, thank you very much for these. Alas my distribution of Linux is a little "bleeding edge" (Arch Linux) and so time fails to compile due to errors in the DateStrings.cpp.

I have fixed the errors (due to declarations that the compiler now insists must be constant) which were very minor but thought I would share to get them combined into the library.

Please see diff file:

Code:
diff DateStrings.cpp DateStrings1.cpp 
41c41
< PGM_P monthNames_P[] PROGMEM = 
---
> PGM_P const monthNames_P[] PROGMEM = 
58,59c58,59
< PGM_P dayNames_P[] PROGMEM = { dayStr0,dayStr1,dayStr2,dayStr3,dayStr4,dayStr5,dayStr6,dayStr7};
< char dayShortNames_P[] PROGMEM = "ErrSunMonTueWedThrFriSat";
---
> PGM_P const dayNames_P[] PROGMEM = { dayStr0,dayStr1,dayStr2,dayStr3,dayStr4,dayStr5,dayStr6,dayStr7};
> const char dayShortNames_P[] PROGMEM = "ErrSunMonTueWedThrFriSat";