Pop up calander

Pop up calander

When I created a new invoice a calendar pops up when I go to enter the invoice date, I would like to be able to bring up the Calendar when I am adding items to an invoice. I have 2 customers that I invoice at the end of the month but do quite a lot of work for so have a lot of items on the invoice. On each one I put where and what the work was done then the date. On my computer I can just click on the clock to see a small calender but I cannot do that in the phone app.