Workflow timebased condition


I don’t understand how to work effectively with timebased conditions in Workflow.
In contacts, I’ve added a custom dropdown field which determines the moment I must call back a contact (in 1 week/in 1 month/etc…).
I want to receive an email when this field is modified, accordingly to the corresponding field

Here is my workflow for a reminder 2 weeks after the moment I modify the field:

  • WorkFlow Module : Contacts
  • Run : always
  • Run On : All Records

Condition 1 :
Module | Field | Operator | Type | Value
Contacts | Date modified | Less than or equal to | Date | Now | - 2 weeks

Condition 2 :
Module | Field |Operator | Type | Value
Contacts | [customDropfield] | equal to |Value | [custom : call in 2 weeks]

Action : send mail etc…

My cronjob is working, schedulers too, but it doesn’t work, any ideas how to deal with that ?
Again, sorry for my english, I’m french !
Thanks in advance,

In other words : I’d like to set a reminder when one of my contacts dropdown field is on the same state for a certain time.
Actually, none of my workflow involving a time condition has ever worked.
One of two things must be true : either I make a mistake in my workflow conditions configuration (but I’ve tested a lot of combinations), or there’s an external cause to the fact it never triggers…

Nobody can help ?