In this basic approach, a flow author can store an offset in a flow level variable and apply that to UTC DateTime values used in flow calculations. In the following example, the offset is stored in Flow.HourOffset:

Flow.LocalDateTime = AddHours(GetCurrentDateTimeUtc(), Flow.HourOffset)

When a time zone springs forward or falls back, change the value in Flow.HourOffset and republish the flow. This simple logic may be sufficient for your organization. Some timezones; for example, Arizona and Hawaii, do not spring forward or fall back, so a hard-coded offset is sufficient.

Additionally, some time zones spring forward or fall back by 30 minutes, rather than one hour. In those instances, use AddMinutes instead of AddHours to apply the appropriate offset. If you have a local time that deals with DST, change the value stored in the variable used for the offset as appropriate when the time springs forward or falls back. In the example above, that means changing the value in Flow.HourOffset and republishing the flow when the time springs forward or falls back.

To avoid the task of republishing the flow whenever the time zone springs forward or falls back, as in the previous example, you can use collection variables to consider offsets for a time zone. While this option requires more work initially, it eliminates the need for managing offsets stored in flow-level variables and offers more simplicity than using expressions.

This method uses a parallel array approach and saves the desired offsets that consider the bias offset for a timezone given a UTC DateTime value. This example is a setup of integer collection variables for Eastern timezone DateTime value calculations. 

* Add more entries for call flows that run past the year 2020.

This collection is a set of UTC DateTime values for when the Eastern time zone springs forward or falls back. Now, build a task that, when a flow initiates, looks for a local time based on DST and time zone considerations:

1. Determine the UTC DateTime value for which the flow author wishes to get a local DateTime. For example, use an Update Data action or a Flow.StartDateTimeUtc to save off GetCurrentDateTimeUtc() to Flow.UtcDateTimeToCheck, or in this case, use Flow.StartDateTimeUtc.
2. Add and configure a Loop action:
   1. Starting at Index 0, loop through the Flow.UTCDateTimeCollection.
   2. For the first value found in Flow.UTCDateTimeCollection greater than or equal to Flow.UtcDateTimeToCheck, save the corresponding minute offset from the same item index in Flow.LocalTimezoneMinuteOffsetCollection to Flow.MinuteOffsetToApply.
3. After the loop, if no value is assigned to Flow.MinuteOffsetToApply, assign a default minute offset; for example, 300. In this situation, the UTC DateTime value for checking time does not have an entry greater than or equal to it in the Flow.UtcDateTimeCollection variable.
4. Next, use the following expression to obtain the local time from the algorithm above:

   Flow.MyLocalDateTimeToUse = AddMinutes(Flow.UtcDateTimeToCheck, Flow.MinuteOffsetToApply)

You now have a local time with the appropriate bias applied to it that you can use for calculations. The applied bias is based on the lookup value in the Flow.LocalTimezoneMinuteOffset collection.

Although the expression approach is more complex, this method does not require hard-coded DateTime values in to a collection along with a corresponding offset integer collection. However, expressions can prove more complicated when adapting a particular time zone, especially if springing forward or falling back causes a day change in the UTC DateTime calculations.

AddMinutes(Flow.StartDateTimeUtc,
     (
          If(Flow.StartDateTimeUtc >= GetDayOfWeekOccurrence(1,2,Year(Flow.StartDateTimeUtc),3,1,0,0)
               and Flow.StartDateTimeUtc <= GetDayOfWeekOccurrence(1,1,Year(Flow.StartDateTimeUtc),11,1,0,0),
               -240,
               -300)
     )
)

(
      (Month(Flow.UtcDateTime) > 3)
        or
      (Month(Flow.UtcDateTime) == 3 and Month(AddDays(Flow.UtcDateTime, -7)) == 3 and Month(AddDays(Flow.UtcDateTime, -14)) == 3)
        or
      (
        (Month(Flow.UtcDateTime) == 3 and Month(AddDays(Flow.UtcDateTime, -7)) == 3 and Month(AddDays(Flow.UtcDateTime, -14)) == 2)
          and
        (DayOfWeek(Flow.UtcDateTime) > 1 or (Hour(Flow.UtcDateTime) >= 7))
      )
    )
    and
    (
      (Month(Flow.UtcDateTime) < 11)
        or
      (
        (Month(Flow.UtcDateTime) == 11 and Month(AddDays(Flow.UtcDateTime, -7)) == 10)
          and
        (
          (DayOfWeek(Flow.UtcDateTime) == 1 and Hour(Flow.UtcDateTime) < 8)
            or
          DayOfWeek(Flow.UtcDateTime)!=1
        )
      )
    )