When I started working the company automatically enrolled me in our 401k. The default was 3% contributions and directed entirely into a company-designed "moderate portfolio". I presume this moderate portfolio fund is comprised of some mixture of stocks/bonds, but I'm really not sure. The expense ratio is ~1%. I left everything at the defaults, as I was lazy and I wanted money to pay off student loans and for a house down payment.
When our company started 401k matching I increased my contributions to 4% to get the full match. I still had student loans and I thought if I wanted any chance of retiring early I shouldn't tie up my money in a 401k. I know about the Roth IRA conversion now, but I didn't then.
Eventually I took a little interest in where my 401k contributions were going. Diversification is good, right? I changed my allocations to go a little into each fund that looked like it had decent past performance, maybe around 10 different funds. I left my current holdings alone, choosing not to rebalance. I paid off my student loans, but didn't increase my contribution percentage.
Last year I discovered MMM and learned about expense ratios, index funds, and Roth IRA conversions. I further adjusted my allocations to go primarily into the one low expense ratio fund my company's 401k offered, VFIAX (Vanguard 500 index). But again I left my current holdings alone, as I was worried about overvaluation of the stock market and wanted to still be somewhat conservative. I also increased my 401k contributions and I am on track to hit the federal maximum this year.
I decided that ultimately I wanted my 401k to be 100% VFIAX, but I didn't want to do it until there was a good correction. October last year would have been a good time to do it, but it sort of caught me off guard. Then this month these forums went crazy over the sudden dip. If I hadn't been actively reading I probably wouldn't have even noticed.
So it was time. I figured this was a good opportunity to rebalance my 401k, something I wanted to do anyway. So on August 25th I logged in and directed my 401k to rebalance to 100% VFIAX. It is now looking like I might have picked the exact lowest day of the SP500 (assuming it doesn't drop again, of course), effectively timing the market! Though all I really wanted was to bring my 401k in line with my investment policy.
This is more a story about the long road I took to finally take control of my 401k than about actually timing the market. Sorry for the clickbait title. ;)