Since this thread started, I have made a special point of checking the published twilight and rise/set times online and in comparison to some older printed resources...they are, for my location, accurate.
I have also noted the actual times of rise/set, and the times of times of the civil, nautical and astronomical twilights (yes, there are three, and they are different)...and they seem to be right on schedule here in Central Illinois, US of A.
Now then, there are a number of natural phenomena that can affect darkness (noctilucent clouds, stratospheric dust caused by major volcanic eruptions, etc.)...But I've not seen any such effect here in the last few days, nor have I heard about any on any other media.
If you think it's real, start keeping records and otherwise documenting it...