You need to stare at your computer screen ALL day and ALL night, like this...
In all seriousness, there are no set times or days for any of the
Disneyland Resorts table service restaurants.
Some have released by 3am and all the prime spots have gone by 7am. Some have been coming out at 6am to 8am. Then some like Oga's and Carthay Circle came out late afternoon and I was lucky enough to be browsing DIS to see the messages that they were open.
As for the days out, some have been 60, some at 45 and some get released a couple of days after the announcement of their re-opening.
Hopefully now that most all these table service restaurants are reopened by now, there might "hopefully" be a little bit more schedule to these releases.
Bottom line, if doing it yourself, alot of starring and refreshing from 60 days on in of your trip. Or just Google "disneyland table service notification" and several paid services are available to send you a notification when available. After that it's a matter of how fast you are to login and snag the date/time you want.
Best of Luck!