recomputed cleanly for -2, -1, +1.trading days. +1=first day of each month, -1 means last day of a month. Using Norgate data and Chatgpt to cacuate.

Signal data = prior trading day before the trading day, so prior day's close and volume to do the math
Trade = selected offset day close
Timing rule = SPY > 325-day SMA; if it isn't, you go to cash on trade day  SMA is simple moving average
Other criteria for entry: 
Overlap of picks between two different 5 stock strategies are bought, but only  if 5 day share volume is greater than 50% of the 60 day trading share volume ave

Full available data period: Oct 1993–Apr 2026  mdd=max drawdown   UI=Ulcer Index  CAGR=compound annual growth rate    "Longest recovery" is greatest # of days to make back any loss of -10% or greater in that strategy     SPY=S&P500   NDX=Nasdaq100  "Best day" is the day with best CAGR to do your buys (and sells) for that strategy

Strategy
Best day	CAGR	Sharpe	Beta	UI	MDD	Longest recovery from any -10% or worse loss
SPY	+1	10.65%	0.635	1.00	14.66	-55.2%	1020d
NDX	+1	13.72%	0.611	1.21	40.16	-82.9%	3292d
9m Momentum 
Top 5	+1	27.94%	0.890	0.90	19.82	-56.4%	1199d
PHL180 
Top 5	-1	29.96%	0.991	0.81	17.16	-55.5%	1162d
Overlap + 
volume 
entry	-2	37.97%	1.061	0.82	17.72	-45.2%	462d

Post-1999
Strategy	Best day	CAGR	Sharpe	Beta	UI	MDD	Longest recovery
SPY	-2	 7.98%	 0.495	1.00	16.21	-55.2%	1020d
NDX	-2	 7.54%	 0.403	1.21	44.60	-82.9%	3292d
9m Momentum 
Top 5	+1	21.24%	0.750	0.83	21.38	-56.4%	1199d
PHL180 
Top 5	-1	22.36%	0.825	0.72	18.73	-55.5%	1162d
Overlap + 
volume 
entry	-2	27.61%	0.878	0.73	19.18	-45.2%	462d

So for the practical version people might actually use monthly, the best tested day was -2, not +1. 6% cagr improvement from 9 month top 5 with SPY timing rule. Almost 4X index fund return despite owning only 5 stocks