Valid values for the value
argument are the same as specified in the
Details section of strptime
.
An xts object's tformat
is NULL
by default, so the index will be
formatted according to its tclass
(e.g. Date
,
POSIXct
, timeDate
, yearmon
, etc.).
tformat
only changes how the index is printed and how the row
names are formatted when xts objects are converted to other classes (e.g.
matrix
or data.frame
. It does not affect the internal index
in any way.