data1
   month1 year
1: 1    2014
2: 2    2015
3: 3    2016
..

data2
   month2
1: 4
2: 5
3: 6
..

for(i in 1:10){
s1_i  = sample(data1[month = i ], 100, replace=TRUE)
s2_i = sample(data2[month > i ], 100, replace=TRUE)
new_i = cbind(s1_i,s2_i)
 }
allsamples = rbind(new_1,new_2,new_3,...)