A few of the Adbeat API methods allow you to specify a date or a date range as part of their parameters. Here's how to properly format those parameters.
Dates should be in the YYYY-MM-DD format (e.g., 2014-12-31).
Date ranges should be specified in this format: [YYYY-MM-DD TO YYYY-MM-DD].
In most methods, the maximum span allowed between dates is 8 days.
http://api.adbeat.com/v3/{api-key}/adMetrics?firstSeen=2012-12-24
http://api.adbeat.com/v3/{api-key}/adMetrics?firstSeen=[2012-12-24%20TO%202012-12-31]