Triggering workflow automatically by a particular date

I am new to Sharepoint. I have a list where the date is given in a column and on that particular date the workflow must automatically trigger.

I went to sharepoint designer but couldn't set th开发者_开发百科e value to date. 

How do I trigger a workflow automatically by a particular date??

Please help. I would really appreciate your help.

Thanks!! Sharmi

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My best bet would be to just start the workflow when the item is added / edited and then add a waitactivity that waits for the period of time from now till the set date.