Field Equipment: Standard vs. Daylight Savings Time


We are often asked by our clients why we always program field data collection systems in Standard time, and why we never collect or show data in Daylight Savings Time. The main reason is for long-term consistency, and it usually only gets appreciated years later when all of that great data gets looked at by someone doing a multi-year study.  Here’s an example:


A client has been using FlowWorks for several years, and is now ready to do some sewer inflow & infiltration (I&I) analysis work. The client downloads a block of data, or uses the FlowWorks I&I analysis tool for this purpose.


When you do this type of analysis, you remove a dry weather flow pattern template from the total flow data. It is essential that all of the data be in Standard Time, otherwise you run the risk of using dry and wet weather templates that are shifted relative to each other by one hour (dry weather often being taken when Daylight Savings Time is in effect, while wet weather events are often during Standard Time). The result is sometimes subtle and difficult to see, but often leads to the wrong inferences being generated in the analysis.


 We’ve seen this happen in many other situations. For example:

  • Operations staff will look at data and want to know when the early morning low sewage flow comes, in order to plan for some maintenance work in the pipe. Not being sure if the data is in Standard or Daylight time causes confusion. With FlowWorks, nearly everything is always in Standard time.

  • Comparing data from two different rain and storm sewer stations (one running in Standard Time, the other in Daylight) causes confusion and puts a one-hour error on the timing of the rain peak relative to the storm peak.


Whenever we have the choice, we always run our data collection platforms in Standard Time as we feel it is a best practice, and avoids as much confusion as possible. It is true that there is an inconvenience associated with all of the data being stored in Standard Time, usually when the data is being used for very casual review by someone who is not used to Standard Time, or if trying to pin down the time that an actual event (such as a sewer overflow) occurred. However, we feel the long-term benefits of keeping everything on the same time signal outweigh the inconveniences.


If you find that you absolutely must have the correction for Daylight time applied to your data, talk to us! We may be able to provide you with a workaround.



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