Time Conversion Functions

[cyanskies]

I'd like to add functions to convert between the datetime types in toml and std::chrono types.

[cyanskies]

Could look at storing time as a std::tm? Will have to look at how other libs handle time.

[cyanskies]

std::tm doesn't have members to store the time offset, but can store all the other data for a localtime and date. So we'd need to store both a std::tm and an extra offset struct.

[cyanskies]

To convert our time types to std::chrono we can follow the following procedure:

• Fill out a std::tm struct with our data
• convert the std::tm to a std::time with std::mktime
• convert to a system_clock::time_point with std::chrono::system_clock::from_time_t

The reverse could be done with:

• to_time_t
• gmtime or localtime
• extract the data

We could also limit it to converting to time_t. Should also look into using std::put_time and std::strftime to do most of the date formatting rather than hand rolling it in to_string_visitor.