It is in the latest month. You will be only on the ranking if you played at least one game in the latest 28 days.
The same question about DM was ask in the other thread about also a different game mode. Let me quote my answer:
2v2v2v2 and FFA were never that popular as DM was in the past. Since 2v2v2v2 and FFA were there frome the start from AoE II, i dont think they will become much more popular. So i dont believe in the argument ‘I actually think they can become popular’. That can only be used for modes like empire wars or battle royale. If there is a game mode for which ranked could work, then it is EW in my eyes. If Redbull continu with their EW tournaments, i see the pros playing on that ladder as well. But that is a completely different subject. Not something for this thread.