My understanding is that the IRS applies the January 1 birthday rule if it benefits the taxpayer. So, for example, if your 65th birthday is January 1, 2026 you get the increased standard deduction for 2025. That's why Form 1040 for 2025 asks if you were "born before January 2, 1961." But having to take an RMD does not benefit the taxpayer, so if your 73rd birthday is January 1, 2026, you do not have to take an RMD for 2025.
