date to string and number before reaching sum
format - tests
fix - date to str
improve coverage
tests for number_before_reaching_sum
passes an edge case!
fix - tests for 8
improve - 8
number_before_reaching_sum
fix - number before reaching sum
rename - items
add - extra base-case
add - more tests
test - month range
add - month_range
add - oldest
first pass
fix - errors
tests
space