Many method arguments and properties describe time periods, such as update rates, delays, timeouts etc. For consistency, they are all integers, and they are expressed as number of milliseconds. In OPC UA, an exception to this rule is for the maximum age of value (for reading), which is a floating point number in order to allow a finer precision.

Some method arguments and properties (but only some – see Reference documentation for each method argument or property) allow a special value that represents an “infinite” time period.

In OPC Data Client “Classic” and OPC Data Client-UA, the value for “infinite” time period is equal to Timeout.Infinite (from System.Threading namespace).

Note: Time periods should not be confused with absolute time information, which is usually expressed by means of DateTime structure.

In OPC Data Client-COM, the value for “infinite” time period is equal to -1.

Note: Time periods should not be confused with absolute time information, which is usually expressed by means of Windows DATE data type.