^(?:.{0,3}(?:[^\d\n]|$)|\d{4}(?:[^-\n]|$)).*

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第一个替换匹配前4个字符中有一个不是数字的字符串。第二个选择匹配4位数字，后面不跟连字符。
DEMO

这里有两个Python的例子。一个用于匹配日期，另一个用于不匹配日期：

import re

examples = ["2023-12-25 is my favourite day of the year", "I like to eat candy", "2001- a space odyssey was released in 1968", "1969 was a great year for dad rock"]

date_pattern = r"^\d{4}-.*"

anti_date_pattern = r"^\D+.*|^\d{4}[^-].*"

start_with_year_dash = [re.findall(date_pattern, example) for example in examples if re.findall(date_pattern, example)] # [['2023-12-25 is my favourite day of the year'], ['2001- a space odyssey was released in 1968']]
dont_start_with_year_dash = [re.findall(anti_date_pattern, example) for example in examples if re.findall(anti_date_pattern, example)] # [['I like to eat candy'], ['1969 was a great year for dad rock']]

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