Return a daily or business day ti corresponding to a
specified position within a time index.
tiDaily(xTi, offset = 1)
tiBusiness(xTi, offset = 1)a ti object or something that the ti()
function can turn into a ti object
for ti xTi, a number in the range [0,1] telling where in the
period represented by x to find the day. 0 means the first
day of the period, 1 the last day of the period, and fractional
values for in-between day.
tiDaily converts its first argument to a jul using the
offset provided, and returns a daily ti for that day.
tiBusiness converts its first argument to a jul using the
offset provided, and returns a "business" ti for that day.