Normal suggestions are designed to be aware of how often you have typed something, and to respond. The down side is that they are not so "clever" or context aware.
Here you are seeing a Smart Suggestion, which are designed to be type specific, but by default they only offer basic options. You can add a snippet to extend the options suggested, on a type by type basis, so in this case, open your VA Snippet editor and paste in the following XML to add a smart suggestion entry for the C# DateTime type, adding the Now method:
<VA_Snippet>
<Language>C#</Language>
<Title>SuggestionsForType DateTime</Title>
<Shortcut />
<Description />
<Code>DateTime.Now</Code>
</VA_Snippet>
This will take effect as soon as you accept the new snippet.
This is listed in the documentation, but I am not sure how many people realise you can do this:
https://support.wholetomato.com/default.asp?W172
