Hostie
I think you'll find the change of flight number coincides with a change of departure time that will be incorporated into the new summer schedule (hence the date)
That is cr*p. Flight times change with the seasonal schedules all the time without flight numbes changing, often for good reason - manager says to secretary - book me on BA223 on thursday etc.
The change is to try to remove the wheat (the BA flight to IAD number 223) from the chaff (possible terrorist chatter about 223) and re-introduce stability to the schedule for this flight.
CargoONe
Remember we are talking about Americans here, 223 = 23rd Feb = today. 293 = 3rd of the 29th month or 93rd of Feb.