auto x = YearMonth(2020, Month.mar);
auto x1 = x + 1;
assert(x1 == YearMonth(2020, Month.apr));
auto x2 = x + 2;
assert(x2 == YearMonth(2020, Month.may));
auto x3 = x + 3;
assert(x3 == YearMonth(2020, Month.jun));

auto ym = YearMonth(2020, Month.mar);
ym += 2;
assert(ym == YearMonth(2020, Month.may));
ym -= 1;
assert(ym == YearMonth(2020, Month.apr));

import mir.ndslice.topology: iota;

static immutable result1 = [YearMonth(2020, Month.mar), YearMonth(2020, Month.apr), YearMonth(2020, Month.may), YearMonth(2020, Month.jun)];
static immutable result2 = [YearMonth(2020, Month.mar), YearMonth(2020, Month.may), YearMonth(2020, Month.jul), YearMonth(2020, Month.sep)];

auto ym = YearMonth(2020, Month.mar);

auto x = ym + 4.iota!uint;
assert(x == result1);

// every other month
auto y = ym + iota!uint([4], 0, 2);
assert(y == result2);