Czesław Piątas was promoted to the rank of general in the year 2000. This information is supported by a document from the United Nations Disengagement Observer Force (UNDOF), which mentions his promotion during that year. Additionally, he is referred to as "General Czesław Piątas" in various sources from around the same time, indicating that he held the rank of general by then. For more detailed information, you can refer to the UNDOF document here.