Hi I have a an object which contains a ptime and an int mask. The mask tells me that regardless of the value stored inside the ptime object, I should display the ptime as such. If you look at the code below (set_fmt function), I set the format of a date_facet object according to some bitmasks. I now want to use this date_facet together with my ptime to output the ptime value to an outputstream? I don't want it to change the outputstream's settings for ALL ptime values, just for this single instance All the examples use a date_facet allocated on the heap, and use std::cout.imbue(...), whereas I'm looking for functionality similar to strftime... is this possible? eg: class expiration { enum expiry_mask { expiry_null = 0x00, expiry_year = 0x01, expiry_month = 0x02, expiry_day = 0x04, expiry_hour = 0x08, expiry_minute = 0x10, expiry_second = 0x20, expiry_date = 0x07, // yyyy/mm/dd expiry_time = 0x38, // hh:nn:ss expiry_all = 0x3f // yyyy/mm/dd hh:nn:ss }; boost::posix_time::ptime desig; int32_t desig_mask; boost::gregorian::date_facet fmt; public: void expiration::set_fmt(const int32_t mask) { switch(mask & expiry_date) *// strip off time part of mask* { case expiry_null: fmt.format(""); break; case expiry_year | expiry_month | expiry_day: *// display as "**dd Mmm yy"* fmt.format("%d %b %y"); break; case expiry_year | expiry_month: *// display as **"Mmm yy"* fmt.format("%b %y"); break; case expiry_year: *// display as "**yy"* fmt.format("%y"); break; default: break; } } ... some other stuff here ... }; Thanks Steve