In Exodus 20:22-24, God instructs the people concerning burnt offerings:
And yet, in Jeremiah 7:22, he appears to forget about this:
One suggestion is that "the day" literally means a specific 24-hour period, and a different one from the day when Moses spoke to God on Mount Sinai. I'm not sure this is the natural reading: "the day" here seems to mean a more broad and vague period, similar to English phrases like "back in the day when men were men". But it's hard to criticise Biblical literalists for taking the Bible too literally.
On a different tack, Tektonics gives a complicated argument that when God says he didn't speak of burnt offerings, he really means that he didn't place much emphasis on them. Again this is not a natural reading, but may have made more sense in the original Hebrew.
The New International Version instead solves this problem in its own unique way, by adding the word "just" to Jeremiah, so it becomes "I did not just give them commands about burnt offerings". It's clear that the NIV translators have no textual authority for the word "just". However, it seems to be their attempt at getting across what they perceive to be the actual intent behind the words, and perhaps is not as dishonest as it first appears. However, they are definitely interpreting for the reader, when they should really just give a straight translation.