def setup_datetime(self, index=None):
"""
Setup the int based matplotlib x-index to translate
to datetime
Separated out here to share between plot and candlestick
"""
if index is None:
index = self.index
is_datetime = self.is_datetime()
if self.formatter is None and self.skip_na and is_datetime:
self.locator = TimestampLocator(index)
self.formatter = TimestampFormatter(index, self.locator)
self.set_formatter()
# reupdate index
self.locator.index = index
self.formatter.index = index
