<script runat="server">
Platform.Load("core","1");

var deLogDev = DataExtension.Init("XXX-EXTERNAL-KEY-1-XXXXXX");
var deBookings = DataExtension.Init("XXX-EXTERNAL-KEY-2-XXXXXX");
var today = new Date();
var thirtyDaysAgo = new Date();
thirtyDaysAgo.setDate(today.getDate() - 30);

try
{
    var filter = {Property:"LastDepartureDateTime", SimpleOperator:"greaterThan", thirtyDaysAgo };
    var data = deBookings.Rows.Retrieve(filter);
    for (var i=0; i < data.length; i++) {
      var result = deBookings.Rows.Remove(["LastDepartureDateTime"], [data[i].LastDepartureDateTime]);
    }
    var rowCount = data.length;
    deLogDev.Rows.Add({Message:Stringify(rowCount) + " items removed from this DE.",Location:"Remove Old Bookings Script",Date:Now()});
}
catch(ex)
{
    deLogDev.Rows.Add({Message:Stringify(ex),Location:"Remove Old Bookings Script",Date:Now()});
}
</script>