to Ben,
I have another argument about what I wrote before:
Let's notice "Matthew" did not repeat "those days" in 24:21, most likely for not linking his great tribulation with the events of 70:
Mk 13:17-19
And alas for those who are with child and for those who give suck in those days!
Pray that it may not happen in winter.
For (in) those days there will be such tribulation as has not been from the beginning of the creation which God created until now, and never will be.
To be compared with Mt 24:19-21
And alas for those who are with child and for those who give suck in those days!
Pray that your flight may not be in winter or on a sabbath.
For then there will be great tribulation, such as has not been from the beginning of the world until now, no, and never will be.
"(in) those days" is equivalent to "at that time". But "Matthew" did not repeat these words from gMark. Instead he replaced them by "then" ('tote'), which certainly can mean "next", as you did mention "By NT times τότε could mean "then" in the sense of "next" or "thereupon" or "thereafter,"" (and, in gMatthew, 'tote' means "next" in most cases when it is followed by a verb in the future tense).
Essentially, in 24:21, "Matthew" got rid of the equivalent of "at that time" in order to have it replaced by 'tote', which certainly can mean "next".
What matters is the context.
For me the context includes the Pharisees becoming leaders, and that before the great tribulation is over (because that tribulation is followed immediately by the end: 24:29).
Cordially, Bernard