I think I might know why I lost 2 vacation days for each vacation pause in 1 Day games when I recently traveled from CT to Europe, but only 1 vacation day when I traveled to Asia several months ago: all DATES are defined in Pacific Time.
When I went to Asia, I set my PC clock to remain on CT even when in Asia, so that I would know the time at home. But when I traveled to Europe, I allowed the PC to automatically draw the time and date from the Internet.
In addition, to you, Chess.com, 1 DAY (D) does not seem to equal 24 HOURS (H). Instead 1 DAY = 1 DATE. This is obvious from the fact that as soon as an opponent in a 1 D online game moves, the game appears in MY MOVE list with only 23 H, not 24 H for my next move. But a 2 D online game appears with 2 D, which actually gives me 71 hours in which to move, because after the clock "ticks" through 2 days, I have another 23 hours to move.
When a player travels West to East from CT and crosses the International Date Line, she loses a DATE (not 24 hours, and certainly not 23 hours). For example, when leaving CT at 3:00 pm on 1/1 and flying W to Asia on a 24 H flight, the player lands in Asia on Jan 3. (1/3). The player's computer technically never records 1/2 if she permits Windows to change the date and clock as you move through time zones. But if the player retains CT on the computer, 1 DATE is deducted from VAC time, which is logical.
When a player travels East to West from CT and crosses 0 degrees longitude (GMT), she loses several hours. For example, when leaving CT at NOON 12 pm (1/1) and flying E to Europe on a 10 H flight, she reaches EU at 8:00 am on 1/2, while it is still 10 pm 1/1 CT. The player's computer technically adds hours to the DATE, so that the PC has a day that's more than 24 hours long. If the player retains CT on the computer, 1 DATE is deducted from VAC time when compared to PT, but, if not, 2 DATES are deducted compared to PT, even though only 24 H have expired.
So, by forcing my PC to remain on CT, not Asian time, you deducted only 1 VAC day from my total, as expected, but by changing my system clock when I traveled to Europe, you deducted 1 day compared to PT when I turned VAC ON, but deducted 2 more compared to PT when I took off VAC pause and then put it back on within minutes, even though only 24 hours had transpired.
This problem would not have occurred if you calculated days based on 24 hours rather than 1 DATE. This would also fix the problem of 1 DAY games really being only 23 H games and 2 DAY games being 71 hours.