There are certain questions that the Bible advises us to avoid. I’m not sure there is any specific Scripture that says we should ‘spend time’ figuring out the start and end-dates of the Tribulation. I will offer this though.
In the closing chapters of the book of Daniel he has a vision of three figures standing by the Tigris River. One man stood on the far side of the Tigris, one on the close bank and the other clothed in fine linen standing in the center upon the flowing waters (time). One man on the bank asks of the one hovering upon the waters, “How long shall it be until the end of these wonders?” The man clothed in fine linen raised his right hand towards the southern heavens and his left hand towards the northern heavens and swore by the Eternal God. It shall be for a ‘time, times and an half’ and all things would be finished.
Now Daniel understood that the ‘time was long’ (10:1), that it was a prophecy revealing the timing, but he didn’t exactly understand when the end would be (12:8) even after hearing the prophecy. He was told that it’s meaning would be sealed until the time of the end (12:4 & 9), when many would quickly ‘run to and fro’ resulting in an increase of knowledge (12:4) (maybe referring to the internet).
Daniel was very specific as to when the vision occurred (ch. 10), which was Nissan 24, 3225. As to what the person upon the waters was referring to as ‘a time, times and a half’ Daniel knew it was intended to some greater ‘season’ times three and a half, counting from that date. Otherwise, the mystery was to be sealed until the time of the end. Many would be purified and made white and tried (the saved, washed in the blood of the Lamb who suffered persecution). The wicked shall do wickedly and none of them shall understand it; but the WISE SHALL UNDERSTAND. Once that moment is understood and confirmed by the abomination of desolation, as spoken of by Jesus (Mat. 24:15), the 1290 and 1335 day counts begin.
It is for some wise Christian to understand, living in the end-times, just when that countdown occurs I believe according to Dan. 12:10.
Dan 12:9-13 KJV -  And he said, Go thy way, Daniel: for the words [are] closed up and sealed till the time of the end.  Many shall be purified, and made white, and tried; but the wicked shall do wickedly: and none of the wicked shall understand; but the wise shall understand.  And from the time [that] the daily [sacrifice] shall be taken away, and the abomination that maketh desolate set up, [there shall be] a thousand two hundred and ninety days.  Blessed [is] he that waiteth, and cometh to the thousand three hundred and five and thirty days.  But go thou thy way till the end [be]: for thou shalt rest, and stand in thy lot at the end of the days.