Lookup dataset through pop up calendar and date range prob

I created a dataset of a historical tag using two pop up calendars. On the same page I used a chart with historical data of another tag. Based on the 'xtrace 'value from the chart, i intended to display a value from the dataset using ‘lookup’ expression as explained in a previous post .
For some strange reason, when I populate the dataset using pop up calendars , the lookup expression doesn’t work.
But when i fill the dataset using the date range, it works.
Though it is not evident, is there any difference in the way the dataset is populated using the date range and the popup calendar ??
The time stamp format is the same in both types of calendar

Looking forward to a solution.