From 1 September 2008, data on unsuccessful call
attempts must be retained by telecoms operators for between six
months and one year, and then destroyed at the end of the data
retention period.
An unsuccessful call attempt is where a telephone
call has been successfully connected but not answered or there has
been a network management intervention.
The measures apply to all providers of publicly
available electronic communications services and will bring Czech
law into line with EU law.
Law:
Act No. 127/2005 Coll., on Electronic
Communications, Directive 2006/24/EC