ANSI C time functions give a number of seconds since a given date (Jan 1, 1900 UTC), so adding days to the time is simply a matter of adding 86400 * number of days.
As an example, these lines can be pasted and executed into the Interactive Execution window:
#include <ansi_c.h>
static time_t dh;
#include <utility.h>
time (&dh);
DebugPrintf ("Today is %s", ctime (&dh));
dh += 86400 * 50;
DebugPrintf ("New date: %s", ctime (&dh));
CVI offers also some proprietary functions to handle date and time: take a look to Date/Time >> CVI time class in the utility library. AddToCVIAbsoluteTime can be a good function for you to consider.
