In a sentence if we have always,sometimes,daily,everyday,often,never,seldom,frequently,normally,occasionally, generally,usually,regularly etc then we will use present indefinite tense. Example: ♥ He never tells a lie. ♥ He always helps me. ♥ When does karim go to bed normally?. In a sentence if we have yesterday,ago,long,before,once,once upon a time,in the past,long since,last week last month,last night,last year etc then we will use past indefinite tense. Example: ♥ He went to London three years ago. ♥ He did the work yesterday. ♥ When does karim went to bed last night?. just,just now,ever,already,recently,lately etc are used in a sentence so we will use present perfect tense Example: ♥ He have just arrived here ♥ He has already finished the task which has been given by me. ♥ I have come home lately?. If the first part of sentence is present indefinite or present prefect tense and after that since/ as if / as though use in a sentence then last part will be past indefinite.In contrast,If first part is past indefinite then last portion must be past perfect tense. Example: ♥ Ten years have passed since you arrived here. ♥ He came to his house as if they had finished the task. ♥ I come to you as though you became ill.