No, sorry to differ but that is still not right. We are at serious risk of some angry face icons....
TDateTime is a combination of a date and a time. The attributes are: year, month, day (to get the day in this first part); hour, minute, second, millisecond (to encode the time in this second part).
A TDateTime is a double, I don't think it has any date or time specif attributes, instead we should say -
TDateTime is stored as a double, the integer part representing days and the fractional part being fraction of a day. Methods exist in Sysutils (datetimeroutines) that allow reading, writing and calculating with TDateTime, converting to and from a number of formats.
If no one objects, I will make that change.
Davo