The most widely known holiday of the Klingon year is the Day of Honor. Eight Days of Honor have been depicted onscreen or in the books and comics, and one other has been mentioned. Their timings during the year have never been consistent during any of those usages. Fandom has commonly placed the Day of Honor on March 23rd in the Earth calendar, in honor of the airdate of the first appearance of the Klingons in "Errand of Mercy." However this date does not align with any of the specific dates given for the Days of Honor shown onscreen on in the literature.
TOS: Day of Honor- Treaty's Law
TNG: Day of Honor- Ancient Blood
DS9: Day of Honor- Armageddon Sky
VOY: Day of Honor- Her Klingon Soul
DS9 (Young Adult): Day of Honor- Honor Bound
Star Trek Unlimited comic story: "The Warrior"
Marvel DS9 Issue 13: Day of Honor
Voyager episode: "Day of Honor"
The Klingon Art of War
So we are left with only this concrete information on when Days of Honor occur, which is neither consistent about the time of year, nor the duration between celebrations.
Given the fact that the two Days of Honor B'Elanna commemorates are said to be consecutive celebrations (despite the fact that they occur more than one Klingon year apart, and despite the fact that Worf notes another Day of Honor which takes place between them) I decided to divide the four dated celebrations into sets of two. A "High Day of Honor" and a "Low Day of Honor." This accounts for B'Elanna only bothering to take note of the "High Day of Honor", while the "Low Day of Honor" celebrations are only mentioned by Worf and Martok, who would be more observant of a lesser cultural occasion.
High Days of Honor
Low Days of Honor
Under this way of looking at things, it becomes interesting that the two Low Days of Honor could be seen as taking place exactly 1.5 years apart. The High Days of Honor don't seem to take place any notable length of time apart.
Going with the assertion from the Day of Honor novelization that the two Days of Honor B'Elanna celebrates are consecutive High Days of Honor, and acknowledging the fact that the span of time doesn't seem to be any round length in the Klingon calendar system (certainly not one year), I speculate that the High Day of Honor actually takes place once every Boreth year. This seems to be a logical alternative to once every Klingon year, in the absence of any concrete alternative.
Then to account for the multitude of frequent Days of Honor in the early 2370s, and fitting with the fact that the two Low Days of Honor which we know the time frames of could be said to be spaced 1.5 Klingon years apart, I speculate that the Low Day of Honor takes place twice per Klingon year.
I speculate the exact period of a Boreth year is 689.384 Klingon days. This makes the High Day of Honor fall on these dates in the 2370s.
The Low Day of Honor being celebrated twice per Klingon year results in these two dates repeating each Klingon year, based on the date we know from the Deep Space Nine novel.
I would further speculate that if the High Klingon Day of Honor falls within the same Klingon month as a Low Day of Honor, the Low Day of Honor is abrogated.
This results in these dates for all Klingon Days of Honor in the 2360s- 2380s.