I’m just going by the sunrise/sunset times and the date/time stamps given by the new forecast API for my Tempest (Center Hill, FL):
forecast":{“daily”:[{“day_start_local”:1611032400,“day_num”:19,“month_num”:1,“conditions”:“Clear”,“icon”:“clear-day”,“sunrise”:1610886084,“sunset”:1610924108,“air_temp_high”:68.0,“air_temp_low”:32.0,“precip_probability”:10,“precip_icon”:“chance-rain”,“precip_type”:“rain”},{“day_start_local”:1611118800,“day_num”:20,“month_num”:1,“conditions”:“Clear”,“icon”:“clear-day”,“sunrise”:1610972472,“sunset”:1611010558,“air_temp_high”:70.0,“air_temp_low”:41.0,“precip_probability”:10,“precip_icon”:“chance-rain”,“precip_type”:“rain”},{“day_start_local”:1611205200,“day_num”:21,“month_num”:1,“conditions”:“Partly Cloudy”,“icon”:“partly-cloudy-day”,“sunrise”:1611058859,“sunset”:1611097009,“air_temp_high”:72.0,“air_temp_low”:45.0,“precip_probability”:10,“precip_icon”:“chance-rain”,“precip_type”:“rain”},{“day_start_local”:1611291600,“day_num”:22,“month_num”:1,“conditions”:“Partly Cloudy”,“icon”:“partly-cloudy-day”,“sunrise”:1611145244,“sunset”:1611183460,“air_temp_high”:75.0,“air_temp_low”:54.0,“precip_probability”:10,“precip_icon”:“chance-rain”,“precip_type”:“rain”},
… trimmed …
For the first forecast day (today):
1611032400 would be 1/19 12:00 am (correct)
1610886084 would be sunrise 1/17 7:21 am (2 days prior)
1610924108 would be sunset 1/17 5:55 pm (2 days prior)
But if you look ahead 2 forecast days for 1/21 the sunrise/sunset times are for 1/19