how to define 'his day' and 'days of the Son of man' (Luke 17)

This question is a spin-off from 'Could I get a Post Tribulation view if possible on the following....'

https://www.sermonindex.net/modules/newbb/viewtopic.php?topic_id=37386&forum=36&220

Luke 17

20 And when he was demanded of the Pharisees, when the kingdom of God should come, he answered them and said, The kingdom of God cometh not with observation:

21 Neither shall they say, Lo here! or, lo there! for, behold, the kingdom of God is within you.

22 And he said unto the disciples, The days will come, when ye shall desire to see ONE OF THE DAYS OF THE SON OF MAN, and ye shall not see [it].

23 And they shall say to you, See here; or, see there: go not after [them], nor follow [them].

24 For as the lightning, that lighteneth out of the one [part] under heaven, shineth unto the other [part] under heaven; so shall also THE SON OF MAN BE IN HIS DAY.

25 But first must he suffer many things, and be rejected of this generation.

Luke 17:26 And as it was in the days of Noe, so shall it be also in THE DAYS OF THE SON OF MAN.

These references remind me of

Luke 13

31 The same day there came certain of the Pharisees, saying unto him, Get thee out, and depart hence: for Herod will kill thee. 32 And he [Jesus] said unto them, Go ye, and tell that fox, Behold, I cast out devils, and I DO CURES TODAY AND TOMORROW AND THE THIRD DAY I SHALL BE PERFCTED.

33 Nevertheless I must walk TO DAY, AND TO MORROW, AND THE [DAY] FOLLOING: for it cannot be that a prophet perish out of Jerusalem.

[34 O Jerusalem, Jerusalem, which killest the prophets, and stonest them that are sent unto thee; how often would I have gathered thy children together, as a hen [doth gather] her brood under [her] wings, and ye would not! 35 Behold, your house is left unto you desolate: and verily I say unto you, Ye shall not see me, until [the time] come when ye shall say, Blessed [is] he that cometh in the name of the Lord.]

So... what did Jesus Christ mean by 'his day' and 'one of the days of the Son of man'?

Any other light on this is appreciated. Thanks to all.

This is interesting from Stong's, for 'days' (Luke 17).

New Testament Greek Definition: 2250 hemera {hay-mer'-ah}

from (with 5610 implied) of a derivative of hemai (to sit, akin to the base of 1476) meaning tame, i.e. gentle;

TDNT - 2:943,309; n f

AV - day 355, daily + 2596 15, time 3, not tr 2, misc 14; 389

1) the day, used of the natural day, or the interval between sunrise and sunset, as distinguished from and contrasted with the night

1a) in the daytime

1b) metaph., "the day" is regarded as the time for abstaining from indulgence, vice, crime, because acts of the sort are perpetrated at night and in darkness

2) of the civil day, or the space of twenty four hours (thus including the night)

2a) Eastern usage of this term differs from our western usage. Any part of a day is counted as a whole day, hence the expression "three days and three nights" does not mean literally three whole days, but at least one whole day plus part of two other days.

3) of the last day of this present age, the day Christ will return from heaven, raise the dead, hold the final judgment, and perfect his kingdom

4) used of time in general, i.e. the days of his life.