order.by requires an appropriate time-based object

PCEP <- xts(us_macro_quarterly_1_$PCECTPI, us_macro_quarterly_1_$Date)["1957::2004"]
Error in xts(us_macro_quarterly_1_$PCECTPI, us_macro_quarterly_1_$Date) :
order.by requires an appropriate time-based object

why does order.by requires an appropriate time-based object appear