Create a formula field that will trigger your automation for each record. The following formula will count down how many minutes until the “send time” (12pm GMT)
DATETIME_DIFF(
DATEADD(DATETIME_PARSE(DATETIME_FORMAT(TODAY(), "YYYY-MM-DD")), 12, "hours"),
NOW(),
"minutes"
)
Set the Automation trigger to be when the formula field is equal to or less than zero. If you have 50 users, the Automation will run 50 times per day to send the email out to everyone individually.