Problem with saving files....

hi, i am sure there is a very simple fix to this so i would be very grateful if someone could point me in the right direction. when i save new files sometimes (approx 70%) of the time it appears under 'no date'

so for example my download folder is where i store all my temporary files. often i will create an image, go to save it and instead of appearing at the top of my downloads in todays additions, it goes at the very bottom under a new heading 'no date'.

whats bizarre is it will then have a date and be in the correct place when i use the mac again the next day.

new user! please be gentle...

 

anybody.....