When we use some time adverbials (On Friday) in a sentence we do not know if the Friday was in the past or in the future.
Is it going to be the blue or green circle?
The way we know is from the verb used in the sentence.
On Friday + I went to the gym. We know this is the past because of the verb 'went'. So, it's the blue circle?
On Friday + I will go to the gym. We know this is a future plan because of the future form, 'will go'. So, it's the green circle.
We can also make the time adverbial mean that is every Friday by using the present tense verb.
On Friday + I go to the gym. Using the present tense verb means that every Friday the subject goes to the gym.
Try these: past, present (meaning every day) or future:
On Sunday I go to the supermarket.
On Tuesday I ate a hamburger.
On Saturday I drink a glass of red wine.
On Monday I went to the bank.
I got-up at 5:00am on Sunday.
My wife went to bed at 11pm on Saturday.
My daughter goes to bed at 10pm on Friday.