Fixed failing datetime tests.
Fixed failing datetime tests.

The failures were specific to xlsx format spreadsheets. When setting the date time to a string format, we need to round to the nearest second.
pricematch/roo-legacy,visagio/roo,pricematch/roo-legacy,pricematch/roo-legacy,airblade/roo,enemycnt/roo,stevendaniels/roo,malept/roo,myplaceonline/roo,salsify/roo,pabloh/roo,xchanging-mm4/roo,fabien-michel/roo,RobertRehberg/roo,reshleman/roo,maruware/roo,thotmx/roo,roo-rb/roo,culturecode/roo