Any rollover problems are unlikely to be associated with the year 2000 and have other than transient affects on system behavior. The term firmware is used here to represent the logic placed in the controller by the manufacturer. Such firmware may make use of date and time information, but such use is likely to be limited. In general, the statements that manufacturers make about their controllers will encompass all firmware within the equipment, but clarification should be sought. A controller that supports 4 digit dates with proper rollover behavior may contain software which fails to make use of these capabilities.
Controllers typically have scarce resources with respect to storage and processing.
Controllers can be used more efficiently if storage and processing requirements are minimised. This provides a strong motivation to use two digit rather than four digit dates and the practice is quite widespread. Users concerned about controller software should determine which organisation was responsible for its production and then seek the requisite assurances regarding compliance. This is likely to be a considerable problem, not least because such assurances may only relate to specific revisions of the software. This software is sometimes provided by the manufacturer of the controller but it is often provided by an OEM supplying a particular control product.