The present perfect tense is used:-
(1)For an action just concluded when the resulting state is still present,eg:-
I have bought the watch.(Up to now---You to Mary)
With activities completed in the immediate past, just is often used,eg:-
I've just bought the watch. (Friday---->Thursday)
I've bought the watch since Thursday.(modified by phrase)
I've bought the watch just now.(= a little time ago)
I've already bought your watch.
Have you ever thought of such a gift ?
------this morning, this afternoon can be used with a Present Perfect or a Past Tense depending on the time the speaking is made,eg:-
I have bought the watch on Thursday morning.(said during Friday Morning.)
I bought the watch on Thursday (said in the afternoon or evening on Friday.)
(2)For duration of an action which began in the past and continuing to the present moment, eg:-
I have bought the watch for 5 days since Monday. (Friday------>Monday)
Keep up with the good work on Verbs---Tense.