Duration applied before units with integer start

[cliffckerr]

ss.Sim(start=2025, dur=12, unit='month').init()
Out[12]: Sim(n=10,000; 2025—2037)

Duration should be interpreted in months, but it's interpreted in years instead. Compare with:

ss.Sim(start='2025-01-01', dur=12, unit='month').init()
Out[15]: Sim(n=10,000; 2025-01-01—2026-01-01)

[RomeshA]

This should be fixed in #847 with

>>> ss.Sim(start='2025-01-01', dur=12).init()
Out[7]: Sim(n=10000; 2025.01.01—2037.01.01)

and

>>> ss.Sim(start=2025, dur=12).init()
Out[4]: Sim(n=10000; 2025.01.01—2037.01.01)

With the month version being

>>> ss.Sim(start=2025, dur=ss.months(12)).init()
Out[5]: Sim(n=10000; 2025.01.01—2026.01.01)
>>> ss.Sim(start='2025-01-01', dur=ss.months(12)).init()
Out[8]: Sim(n=10000; 2025.01.01—2026.01.01)