I’ve created a report using the Data Composition Schema which displays documents, the grouping is set by Date field (for example 06/07/2011 11:22, 06/07/2011 11:23 and so on). Please suggest a way to make a grouping which does not care about time?

For the Date field use the BeginOfPeriod() function with “Day” period (second parameter).

you can use format setting in the field parameter. I think it the better way, but not a single alternative method.

I have tried to set the Format in Appearance property of the Date field in Data Sets tab, but the report was not grouped by this field and I have separate rows for each document. So I have added an additional field to the query due to I need time in this field in another report.

in a query, which is used as a data source for Data Composition Schema, change "Period as Date" field to "BeginOfPeriod(Period,"Day") as Date" field

Correct, George!