Both me and a friend are having the same problem in MT4 when using the Strategy Tester.
Sometimes I test a currency pair with an EA and it works from Jan 1st, or whatever I set. But sometimes it starts from August or something else and won't load the previous history.
Even if I import tick data from the first day of the year. If I try with a different timeframe it might load the complete set of history, but then if I move back to another time frame it will only use fewer data.
I know there are many spots where the EA should take trades earlier than this dates, so it's not anything wrong with the EA's I'm testing. I guess it's a setting in MT4 that I need to change... but which one?
My friend is having the same problem every now and then he told me earlier today, so I though I should ask here.
I guess there might an answer to this in a previous thread, but not sure what to search for to find the right answer.