Dutch First Division Promotion Rules:
Season is divided in 4 periods, two of 8 matches, two of 9 matches. Every winner of a period will qualify for the play-offs. Previous period-winners don't count in the current period! (they are in it, but you might as well forget about them).
At the end of the season nr 1 promotes directly. Nrs 2 and 3 qualify for play-offs also. If those 3 teams have been period-winners then nrs 4 (5,6,7) will qualify. In practice nrs 2-7 qualify, but there are exceptions.
Play-offs consists of two groups, playing a full competition. Both winners of the groups get promoted.
Group 1
nr 16 Premier Division
nr 3 First Division
1st and 3rd Period winners (or replacements)
Group 2
nr 17 Premier Division
nr 2 First Division
2nd and 4th Period winners (or replacements)
And no, I don't know who thought this out, but I suppose he is in some hospital for the mentally ill.
This system was correctly implemented in CM01/02, and I suppose it still is.
As for Heracles: they have played in the Premier Division, but that's a long time ago, I'm afraid. Nowadays they are not one the top flights. They have permission however from the UEFA to play on artificial grass (I'm groping for the right English term here), so they have their claim to fame too! For further information (in Dutch alas) see
Heracles website