Is there any software/site where you can enter two dates in the past + hashrate, and get the result how many BTC was mined in the period between these two dates?
yes but not exactly . You can go to bitcoin wisdom calculator and play around with settings.
Lets say you want Jan 1 to March 1 2014 .
An antminer s-1 set at 200gh. you do this.
go to this link.
https://bitcoinwisdom.com/bitcoin/difficulty
determine the diff on jan 1 2014.
it was 1,180,923,000 for 1 day jan 1 1 day 200gh earned .08517 x 1 = .08517
it was 1,418,481,000 for 11 days jan 2 to jan 12 1 day 200gh earned .07091 x 11 = .78001
it was 1,789,546,951 for 11 days jan 13 to jan 23 1 day 200gh earned .05621 x 11 = .61831
it was 2,193,847,870 for 12 days jan 24 to feb 4 1 day 200gh earned .04586 x 12 = .55032
it was 2,621,404,453 for 12 days feb 5 to feb 16 1 day 200gh earned .03837 x 12 = .46044
it was 3,129,573, 175 for 11 days feb 16 to feb 28 1 day 200gh earned .03214 x 11 = .35354
TOTAL------------------------------------------------------------------------------------------------------------ 2.84779 btc for jan 1 to mar 1 not including mar 1
A shit load of math for someone that wants to get an idea of what the gear earned
