Date rate limits define the minimum amount of time before a user will be sent a subsequent message in the Campaign series. If you set a date rate limit of 2 days and a user was sent the highest priority message, even if they immediately qualify for the next highest priority message, they will not be sent that message until 2 days after the first one was sent.
Date rate limiting is the final check when determining a user’s eligibility for a message. If a user meets the targeting criteria of (and is lined up to receive) a message, they will not be sent that message until this amount of time has passed since the last message they were sent. Once that amount of time has passed, all message targeting criteria is re-checked and only if a customer still qualifies for that message would they be sent the message. Continuing with the example above, if a user triggers an event that disqualifies them from receiving a message that they were previously eligible to receive (but were not sent because they were date rate limited), they would not be sent that message after the date rate limit had passed because they would not meet the targeting criteria for the message when the messages in the series were re-evaluated.
You can specify a date rate limit by hours, days, weeks or months by clicking the gear icon in your Campaign panel and inputting your preferences in the Settings screen: