Since 2021 arrived, Flot chart begins Jan 1970, still shows current file data at end

Question

My plotted file contains two weeks, dates are explicit:

2021-01-03 22:21:14.636679  20.896
2021-01-03 22:26:14.621113  20.896
2021-01-03 22:31:14.605466  20.873
2