DateTime.Now within a statement

Question

In the below thisIsAlwaysTrue should always be true.

DateTime d = DateTime.Now;
bool thisIsAlwaysTrue = d == d;

But does DateTime.Now work in such a way that isThisAlwaysTrue is guaranteed to be true? Or can the clock change between references to the Now property?

bool isThisAlwaysTrue = DateTime.Now == DateTime.Now;

Answer 1

The clock can definitely change between two back-to-back calls to DateTime.Now;

Answer 2

The DateTime.Now property is volatile, meaning it definitely can change between uses. But the variable you assign it to is not volatile.

So this should always set result to true:

DateTime d = DateTime.Now;
bool result = d == d;

It assigns the value returned by DateTime.Now to the d variable, not the property itself. Thus d will always equal d in that code.

But this will not always set result to true:

bool result = DateTime.Now == DateTime.Now;