2008/7/14 Francesc Alted
After pondering about the opinions about the first proposal, the idea we are incubating is to complement the ``datetime64`` with a 'resolution' metainfo. The ``datetime64`` will still be based on a int64 type, but the meaning of the 'ticks' would depend on a 'resolution' property.
This is an interesting idea. To be useful, though, you would also need a flexible "offset" defining the zero of time. After all, the reason not to just always use (say) femtosecond accuracy is that 2**64 femtoseconds is only about five hours. So if you're going to use femtosecond steps, you really want to choose your start point carefully. (It's also worth noting that there is little need for more time accuracy than atomic clocks can provide, since anyone looking for more than that is going to be doing some tricky metrology anyway.) One might take guidance from the FITS format, which represents (arrays of) quantities as (usually) fixed-point numbers, but has a global "scale" and "offset" parameter for each array. This allows one to accurately represent many common arrays with relatively few bits. The FITS libraries transparently convert these quantities. Of course, this isn't so convenient if you don't have basic machine datatypes with enough precision to handle all the quantities of interest. Anne