Hananiah's sudden death fulfills a dramatic prophecy just two months after a tense public confrontation where he broke the wooden yoke off Jeremiah's neck [ביאור שטיינזלץ]. However, the exact timing of his passing presents a chronological puzzle. He is recorded as dying in that same year, yet the event took place in the seventh month. Because the seventh month marks the start of a new calendar year, it raises the question of how his death could still be counted as part of the year Jeremiah delivered his warning.
The primary approach among commentators explains that Hananiah actually died at the very end of the outgoing year, on the eve of the new year. In a final attempt to make Jeremiah's prophecy appear false, Hananiah instructed his family to conceal his death that day. He ordered them to delay his burial until after the new year had begun, during the seventh month [רש״י, רד״ק, מצודת דוד]. In truth, Jeremiah's hidden intention from the start was that Hananiah would die in one year and be buried in the next. He deliberately kept this detail unspoken so the prophecy could be genuinely tested in the eyes of the people [רד״ק].
Conversely, a simpler understanding of the events suggests there is no contradiction at all. When Jeremiah declared that Hananiah would die that year, he was not referring to the formal calendar year that ends just before the seventh month. Instead, he meant a full twelve-month period starting from the day of the prophecy. Therefore, passing away in the seventh month still fell perfectly within the promised timeframe [רד״ק].