When entering survival data, what should I do with animals or patients that die the first day?

How should survival analysis deal with subject who die immediately after entering the study?

Machim (page 8; reference below) states: "A logically valid survival time must be larger than zero." If the survival time is measured in days, and the initial and outcome event happen the same day, he recommends entering X=0.5 or some other small value (depending on the situation).

If you enter X=0, Prism 4 and 5 (like most programs) ignore the data for those subjects, The survival analysis and survival curve will be exactly the same as it would have been if you had simply not entered the row(s) with X=0. , The only advantage of entering the X=0 row(s) is to better document the data.

Note that Prism 3 got confused with X=0 in survival data, and the resulting survival curves and comparisons were not correct.