According to the patch notes the golden pif cave should open at random times. (see: https://www.naeu.playblackdesert.com/en-us/News/Detail?groupContentNo=8189&countryType=en-us)

I dont know about the opening times in NA, but now that we had this grind spot for the past 5 days I can certainly say that the opening times of this grind zone are NOT random, atleast in EU.
On every single day, other then the patchday where it opened after the servers went live at 15CET, the pig cave always opened at around 2am CET.
Mostly at around 11am CET someone will hit the jackpot and it closes again.

There is no way that anyone with a normal sleep and work schedule can grind there. There are so many better ways to implement a jackpot based grindspot like this to the game and make it accesable for everyone.
For example you can make it so its open 24/7 but only one Jackpot per day can be obtained.
Or make the opening time random within a set timeframe. For example 5pm - 9pm every day.. With this even people in different time zones in EU will be able to attend the "event" atleast a few times per week.

Please feel free to comment your thoughts about this.
I would aspecially like to also hear about the NA opening times. Do you guys have the same problem. What are your experiences with the Pig Cave?

could be a:

 "we need more players at X time! Lets put pig cave in this timeframe lie about it being random so eventually, ppl will figure out the "random" time and it will become a game mechanic and numba goes up at time X"

 "we so smart, stupid players will never suspect anything FFFFFFFFFFFFFF"

Pig cave usually opens 12hrs after it got cleared. With slight deviations on the exact time. So yea at the current times, if it gets cleared fast enough the time for when it's open will tend to be the same most of the time. 
With the next patch, the clear conditions will be made more difficult, so maybe it stays open for longer, giving people with different schedules a chance to play, and making the opening times vary more. We shall see if that brings the fix or if more adjustments are necessary 

Hoping for a change with next patch patch but right now I 100% agree

100% agree, Lets only allow degenerates to grind here. To hell with anyone who actually has a job/responsibilities.  Great work!

It seems pretty transparent the 'jackpot' is a pure fixed-odds RNG.

What this means is, the larger the region pop, the sooner someone hits it, and the cave closes. On EU, one of the largest regions, this is ~1hr - presumably shorter than intended. It's probably balanced on KR pop, for obvious reasons.

The out of hours version is far too much sweat vs not a particularly fun grind. For meh silver. So not, imo, a fix. Also even if it were tuned up to be slightly better, feeling you're paying an (admittedly junk) item to grind a 2nd rate version of the zone purely because you log at the wrong time or are in the wrong region is not a fun feeling.

I really don't know what they were thinking with an open/closed grind spot. They talked so much in designing these new zones with how they wanted to make grind fun and interesting. A zone you cannot enter - is, gasp, not fun. The jackpot mechanic isn't fun either when the odds of you ever getting one are either nil, if you don't log on at the right time, or basically nil, if you're on a high pop server so the cave closes in an hour (oh, and even if you get it, it's hardly mind-blowing).

Just have the thing open 24/7. Keep the rare jackpot, but just - don't close the spot for everyone if someone hits it. I hardly think one person out of 100 an hour getting a ~5b tet acc and 100 dawns is going to break the economy. Baffling design choice. It feels like they had a different original design but then had to pivot last-minute because they didn't forsee something obvious (like PvP trolling potential with their original idea of the statue showering silver for everyone).