Chicken SRFI 19 TODO

- Time -> Date conversion takes account of the state of the converted date
daylight saving time state.

- Date/Time field minimums & maximums (useful for UI)

- epoch access (?)

- +inf, -inf, nan times & dates

- add/roll date field; +/- some field, such as "next week"

- date-iterator; +/- some increment per call

- relative-date; such as "last thursday in june"

- Plugable calendar systems