In row "ts_from (required)" last words in description are:
"For onetime downtimes ts_from must be set as a Unix timestamp, for other types - as a specific time in a week, in seconds, for example, 90000 for Tue, 2:00 AM."
Similar error in row "ts_to ** (required)".
... for example, 90000 for Mon, 1:00 AM.
Calendar for uptime/downtime repeated every week starts from Sunday.
Define uptime or downtime period in frontend for some IT service as interval:
|Sunday 00:00 - Monday 01:00|
Look in to DB table services_times, column:
ts_from contains 0
ts_to contains 90000
Sunday 00:00 is written into table as 0 - so, this is weekly calendar start.
90000 seconds is a one day and one hour, so Sunday 00:00 + 1 day and 1 hour = Monday 01:00 AM