* floats are ever a good idea for storing time. a system i use (no, not excel) has one of its time types defined as a double of days since their epoch. the problem is that it's universally represented in the interface as a timestamp to millisecond precision, and many different values may have the same string representation.
i just ran a quick test, and for a specific millisecond around now, about 13,000 distinct timestamps have the same string representation. if you use that string representation as a serialization of any one of those timestamps, it will always map back to a single float value, which will be only one of those 13,000, meaning the others aren't round-trippable.
the system implements a comparison tolerance for floating point numbers, but this helps only slightly, as only about 1100 of those 13,000 test as equal to the one you get if you enter it as a string.
the end result is that you can have data printing to the screen that you can't actually find in the system because its string representation doesn't match its internal one due to precision issues.
(the solution is not to use the type--they deprecated it in favor of one based on longs of nanos several years ago.)
i just ran a quick test, and for a specific millisecond around now, about 13,000 distinct timestamps have the same string representation. if you use that string representation as a serialization of any one of those timestamps, it will always map back to a single float value, which will be only one of those 13,000, meaning the others aren't round-trippable.
the system implements a comparison tolerance for floating point numbers, but this helps only slightly, as only about 1100 of those 13,000 test as equal to the one you get if you enter it as a string.
the end result is that you can have data printing to the screen that you can't actually find in the system because its string representation doesn't match its internal one due to precision issues.
(the solution is not to use the type--they deprecated it in favor of one based on longs of nanos several years ago.)