How to use たがわず as “Regardless of"

Question

Context: two smugglers arrive at village as part of their current assignment

Rock:それにしても閑散としてるな
Revy:人のいねえゴースト ･ ヴィレッジなのさ
この島じゃ ２ 年も前から戒厳令が敷かれてる
昼夜たがわず治安部隊とゲリラが鉛弾ぶち込み合ってんだ
もっと都会の島にでも逃げちまったんだろここの連中は　　
Rock: It sure is quiet here.
Revy: It's a ghost village with no people.
There's been martial law here for the last two years.
The police and the guerrillas are shooting lead...at each other day and night.
The people here must have run away to more developed islands.

From what I can tell from dictionaries and this post is the form に違わず means something similar to (の)通り, literally "not different from".

I assume that there is a に being omitted. But I also wonder to what degree に違わず can mean can be used like this usage, because here it just seems to mean the same thing as でも ("not different from day and night" doesn't make sense here). 　　

昼夜を問わず and 昼夜を分かたず both mean “ by day and night, day and night, round the clock”, which makes sense because of what 問う and 分つ would mean in this circumstance (irrespective of day and night, without distinguishing night and day). I feel that because 昼夜(に)違わず isn't listed as set expression like the other two that means that this specific usage in the show is irregular. Since (の)通り doesn't seem like a valid interpretation here, how is it used here and how frequently is 違わず used this way?

Answer 1

違う is an intransitive verb meaning "to be different", and 違わず is its negative-adverbial form. But here, 昼夜違わず does not mean "not differently from days or nights" but means "in a way that days and nights are not different/distinguished" or "not changing between days and nights". So I think the omitted particle is probably が or で, not に or を. 変わらず is used in the same way; 昼夜(で)変わらず means "(doing the same thing) day and night".

As for the frequency, BCCWJ has 41 examples of 昼夜を問わず, 11 examples of 昼夜を分かたず, and no example of 昼夜違わず. So 昼夜違わず is rare, but I still feel it's a valid phrase, and Google gives many examples of it.