For planing purposes, can take up to 6 months. I was on Active duty in a staff position, there was an opening for an IMA one organizational level above where I was that was open and already funded. All said and done it worked out really nicely with no break in service (which is huge if you're trying to get promoted on schedule in the Guard or Reserve). I will say though that the timeline was frustrating. Be nice, be patient and follow through with everyone at every step.

Good Luck!