Dropbox and Time machine

Hello,

I am trying to make a backup of a DropBox folder on my AirPort using Timemachine. However when I enter TM and look at the backups from previous dates the content in DB is always that of the current date, having for example files that were created on March 3rd on the TM backup from February 27th. All the other folders work fine.

Has anyone encountered this problem or has an opinion on what may be happening?

Thanks a lot,

JR