This is the 714th most frequent Turkish word.
belirtilen
"Specified" or "stated."
In this sentence, "belirtilen" is used as an adjective modifying "tarihte" (date), to describe it as being specified or indicated.
Belirtilen tarihte toplantıya katılacağız.
We will attend the meeting on the specified date.
In this example, "belirtilen" is used to modify "kurallara" (rules), meaning that the rules are defined or outlined prior to this sentence.
Bu belgeler, belirtilen kurallara uygun olarak hazırlanmalıdır.
These documents must be prepared in accordance with the specified rules.
Here, "belirtilen" describes "adrese" (address), indicating that it is the one mentioned or indicated previously.