use offset parameter instead of calculating bday in cdrom
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@chenyi6758-source is already working on this.
Since Oct 19, 2026.
- #2911 by @chenyi6758-source — open
Assessment
- Difficulty
- 1/5
- Estimated time
- Under an hour
- Newbie friendliness
- 92/100
Research direction
Start at _calculate_simple_day_angle in pvlib/solarposition.py and compare its current calculation with the provided offset=81 example. Replace the explicit birthday adjustment, then run the relevant solar-position tests; completion means the simplified call preserves the existing numerical result.
Written by the indexing model from the issue text.
Description
I believe this line in equation_of_time_pvcdrom:
could be replaced by passing 81 to the offset parameter:
>>> from pvlib import solarposition
>>> import numpy as np
>>> solarposition._calculate_simple_day_angle(122, offset=81)
# 0.7057824591626384
>>> solarposition._calculate_simple_day_angle(122) - (2.0 * np.pi / 365.0) * 80.0
# 0.7057824591626387
and ditto in declination_cooper69:
could be replaced by passing -284 to offset parameter
>>> import pvlib as pvl
>>> import numpy as np
>>> pvl.solarposition._calculate_simple_day_angle(180) + (2.0 * np.pi / 365.0) * 285.0
7.987391732962541
>>> pvl.solarposition._calculate_simple_day_angle(180, offset=-284)
7.987391732962542
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