I believe the Stealth Virus coding time is shorter than it should be, I have all of the benefits for coding time reduction:
Base: 100 days
100 - 50% = 50
50 - 50% = 25
25 - 20% = 20
10 - 10% = 18
Assuming Torn calculates the reduction as I did (each bonus separately, largest to lowest), I should spend 18 days programming the Stealth Virus, but instead I spend 17.
I calculated the Polymorphic virus as well, which got me to 4.5 days, but it's rounded down to 4, which is nice I guess, though the wiki says it's 4.83 days, which technically should be rounded up to 5 instead.
I haven't necessarily waited out and counted the days, but I assume it's not relevant if the following is true on the Torn Wiki: "Viruses always finish coding shortly after 03:25 TC Time." (https://wiki.torn.com/wiki/Simple_Virus along with the other virus pages)