Yes, with caveats. Your Day Pillar (which contains your Day Master) is determined by the date and can be calculated without the hour. Your Year and Month Pillars are also unaffected by the hour.
What you'll miss:
- The Hour Pillar — which reveals your inner world, children, legacy, and hidden dynamics
- The full precision of your chart's roots and God placements
Without the hour, a BaZi reading can still describe your core personality, career tendencies, and broad Luck Cycle timing. Many consultants offer a partial reading based on three pillars. Some can work backward from major life events to deduce the likely birth hour.
If you have a window (morning, afternoon, evening), that helps narrow it. Every bit of precision adds depth.