I am thankful to all of you for volunteering your time.
Your lasts posts are right (Walt2 and steven r). It's a fact that people that have an even numbered address loose one day at the end of a month having an odd number of days (May, July, August and October for the summer season). Because this ruling makes it very simple to remember when one can/can't water his lawn, nobody seems to complain (I myself am one of those with an even numbered address).
If I knew how to program it would be a fairly simple task I think to add that feature (even/odd days) to AHP. But I must stop dreaming, this option is definitely not for me. I am thus looking for a program that allows sequencing my five X10 water outlets on even days even though resetting will be required at the end of a month which has an odd number of days. In my municipality, one can water the lawn when the day is right, from 9 PM till 11:30 PM (in my case, 30 minutes for each outlet). Following Tuicemen's advice, I downloaded X10dispatcher. I noticed a Schedules tab which offers a run every x days option. Choosing 2 for this option appears to offer the possibility to water every second day. But I'm not out of the woods yet because I have no clue how to use/configure this last program and how it is used in conjunction with AHP (if it is). I would much appreciate if someone could explain in simple terms (one step after another) how to use this or theses programs together (AHP and X10dispatcher).
Could you also comment on my purchasing decisions for the control of the five water outlets using a X10 network: I plan to purchase AHP with the CM15A interface, five SR227 (SuperSocket Receptacle) each of which will feed a small 24 VAC transformer required by the water outlet, a PalmPad Remote Control (HR12A) for occasional manual control and a 1:1 Passive Ratio Coupler (XPCP) which allows X10 signals to transit on both live wires of the electrical residential system.
Thank you again.