I haven’t seen him this morning  vs. I didn’t see him this morning.

•  How would you differentiate the above two sentences grammatically.  The first one is constructed in the Present Perfect Tense and the second one in the Past Simple.  At the very outset let me make it clear that both the sentences are correct if used in appropriate situations.

. I haven’t seen him this morning.  ( This sentence is correct if the speaker is saying this while he/she is still in the morning session. i.e  today before 12.00 ‘ o clock noon.  We know that a day has mainly two sessions, viz morning session and evening session.)

.I didn’t see him this morning.  ( This sentence is correct if the speaker is saying this while he/she is in the evening session.  When the speaker is in the evening session, you can consider the morning session something as past.  So at this particular situation, using of Past Simple is justified or necessary.)