Rio de Janeiro is 8.75 hours behind Kathmandu
Best overlap: 4:45 PM to 6:45 PM in Kathmandu is 8:00 AM to 10:00 AM in Rio de Janeiro.
The overlap falls at 4:45 PM to 6:45 PM in Kathmandu, or 8:00 AM to 10:00 AM if you're in Rio de Janeiro. Just 2 hours of shared hours means there's little margin — set 4:45 PM in Kathmandu (8:00 AM in Rio de Janeiro) and start promptly.