Estimating T¡me

This puzzle is part of the Monthly Topic Challenge #1: Restricted Title: xkcd 1xxx

The Oracle has been sending me some weird texts lately. It started a couple days ago and the last one came in this morning. I'm not sure what to do. I'm sure it's a puzzle of some sort but how am I supposed to solve it?

Hint

There is information missing that needs to be filled in.

• The title has an upside down exclamation point in place of a lower case i because a question with the same name already existed and this MTC is restricted title. Commented Jul 22, 2022 at 18:31
• Ha, that puzzle you refer to was produced back in Jan with this precise MTC in mind, just in case it launched that month as originally planned (it ended up being delayed) - two for the price of one now!
– Stiv
Commented Jul 22, 2022 at 21:09
• A similar situation happened during the xkcd FTC, when 2 puzzles based on the same xkcd came out on the same day. In that case, the second author was able to sneakily drop a hyphen. Commented Jul 23, 2022 at 2:41
• Does this have something to do with rot13(RGN/RGQ)? Not sure, since the 'knowledge'-tag is missing. Commented Jul 26, 2022 at 13:18
• @Prim3numbah no, not related to that. Commented Jul 26, 2022 at 16:55

Though I haven't been able to solve the puzzle so far, here are my current thoughts. If anyone could build upon this, that would be encouraged!

More than likely,

the key to this puzzle lies in the times at which the Oracle sends its mysterious messages. We also notice that the minutes part of each time is less than or equal to 26, so we can use the A1:Z26 substitution to transform each number into a letter, as follows.
SE
ON
 G leaving a space for "00"
ES
IN

Cap's hint that

there is missing information to fill in made me slightly more confident in my instinctive approach to the problem, which was calculating the differences between the times as well. Doing so (and applying A1:Z26 again, modulo 26), we get
20:09 -> TI
08:53 -> HA
05:12 -> EL
03:55 -> CC

We see that

there are some sequences of letters that could be relevant -- in particular, putting ES and TI together we get the first four letters of the word estimating, and putting IN and the lone  G together, we get the last three letters.

However,

this is where we get stuck. What function do the other letters serve? Where does the tag come in, beyond A1:Z26? Was taking numbers modulo 26, or even using A1:Z26, the right approach?

This looks like an intriguing puzzle -- can't wait to see it solved!

EDIT:
Wait!

Taking the A1:Z26 sequence from before,
SE
ON
 G
ES
IN
we can add letters to the end of each line (hence "filling in information") to complete the solution:
SEC
OND
 GU
ESS
ING
This gives SECOND GUESSING, which not only is another way of saying "estimating time", but also what this puzzle made me do the entire way.

EDIT 2:
As Cap noted in the comments,

since the first letter in each line corresponded to the hours part of each time, and the second letter in each line corresponded to the minutes part of each time, adding a third letter would literally be "second guessing" -- guessing the appropriate seconds part of each time to complete the solution!

• Your first step is correct and looks exactly like my notes. Also you have correctly understood the cipher tag to the intended extent. So close! Commented Jul 27, 2022 at 1:58
• @cap rot13(V guvax V sbhaq gur fbyhgvba (V rqvgrq zl cbfg!). Bar dhrfgvba -- jrer gur yrggref V nqqrq gb rnpu yvar fhccbfrq gb or qrevirq sebz n fgrc V fxvccrq?) Commented Jul 27, 2022 at 2:32
• Nice your answer is correct and nope, you literally had to rot13(thrff gur frpbaqf (abgr gung gubfr yrggref jbhyq unir orra ercerfragrq ol gur frpbaqf sebz gur gvzrfgnzcf vs gurl jrer gurer)). Commented Jul 27, 2022 at 2:34