ここ数日、各ニュースサイトから日付を取得することにハマってます。
書いてたコードを多少実用的なクラスにしたので公開します。
もちろんサイトによってはボットでのクロールを禁止していますので、使用にあたっては注意してください。
以下のサイトから取れるようにしています。

朝日新聞
日経新聞
産経新聞
読売新聞
毎日新聞
Yahoo!ニュース
CNN
Bloomberg
BBC
Reuter
Wall Street Journal
Forbes Japan
Newsweek
CNN.co.jp
ABC News
外務省
AFP BB
NHK News
日刊工業新聞
EUROPA NEWSWIRE
国連広報センター
OPCW News
HAARETZ
THE DAILY STAR
INDEPENDENT
ジェトロ
夕刊フジ

取得はrequestsライブラリ、パース等はBS4で行い、その後正規表現とdatetimeのstrptimeで日付を取得しdatetime型にしてます。
日付単位で取れるサイトや分単位で取れるサイトなど、粒度はまちまちです。本来日単位で取れるものはdateオブジェクトにするべきなのですが、まあガバいです。変数名の表記揺れなどもひどいですね。あくまで「ざっくりした更新日をなるべく高確率で取得できたら良いな」というスクリプトです。
ここまでしないと更新日の取得ができないのだろうか、という疑問もあり、、詳しい方のコメントをぜひ欲しいところです。。

news_timestamp.py

import bs4
import requests
import datetime
import re
from jeraconv import jeraconv

class ScrapeNewsTimestamp:
    def __init__(self):

        self.headers = {
            "User-Agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36",
            "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8",
        }

    def scrape_return_timestamp_1(self,bs4Obj):
        try:
            #朝日新聞
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select('time')[0].string, "%Y年%m月%d日 %H時%M分")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_2(self,bs4Obj):
        try:
            #日経新聞 時は金なり
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select('time')[1].string, "%Y年%m月%d日 %H:%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_3(self,bs4Obj):
        try:
            #日経新聞 海外金融ニュース
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select('.cmnc-publish')[0].string, "%Y/%m/%d %H:%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_4(self,bs4Obj):
        try:
            #日経新聞 春秋
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select('.cmnc-publish')[0].string, "%Y/%m/%d付")
            return news_timestamp
        except Exception as e:
            return None


    def scrape_return_timestamp_5(self,bs4Obj):
        try:
            #産経新聞 国際
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select('#__r_publish_date__')[0].string, "%Y.%m.%d %H:%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_6(self,bs4Obj):
        try:        
            #読売新聞 国内
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select('time')[0].string, "%Y/%m/%d %H:%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_7(self,bs4Obj):
        try:                
            #毎日新聞 東京朝刊
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select('time')[0].string, "%Y年%m月%d日　東京朝刊")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_8(self,bs4Obj):
        try:        
            #毎日新聞 東京夕刊
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select('time')[0].string, "%Y年%m月%d日　東京夕刊")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_9(self,bs4Obj):
        try:
            #毎日新聞　速報
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select('time')[0].string, "%Y年%m月%d日 %H時%M分")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_10(self,bs4Obj):
        try:
            #毎日新聞　プレミア
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select('time')[0].string, "%Y年%m月%d日")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_11(self,bs4Obj):
        try:
            #Yahoo!ニュース
            bs4Obj = bs4Obj
            m1 = re.match(r'\d{1,2}/\d{1,2}',str(bs4Obj.select('p.source')[0].string))
            tmp1 = m1.group()
            m2 = re.search(r'\d{1,2}:\d{1,2}',str(bs4Obj.select('p.source')[0].string))
            tmp2 = m2.group()
            news_timestamp = datetime.datetime.strptime(str(datetime.datetime.now().year)+tmp1+' '+tmp2, "%Y%m/%d %H:%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_12(self,bs4Obj):
        try:
            #CNN
            bs4Obj = bs4Obj
            m1 = re.search(r'Updated (\d{4}) GMT', str(bs4Obj.select('.update-time')[0].getText()))
            m2 = re.search(r'(January|February|March|April|May|June|July|August|September|October|November|December) (\d{1,2}), (\d{4})', str(bs4Obj.select('.update-time')[0].getText()))
            nes_timestamp_tmp = m2.groups()[2]+m2.groups()[1]+m2.groups()[0]+m1.groups()[0]
            news_timestamp = datetime.datetime.strptime(nes_timestamp_tmp, "%Y%d%B%H%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_13(self,bs4Obj):
        try:
            #Bloomberg
            bs4Obj = bs4Obj
            timesamp_tmp = re.sub(' ','',str(bs4Obj.select('time')[0].string))
            timesamp_tmp = re.sub('\n','',timesamp_tmp)
            news_timestamp = datetime.datetime.strptime(timesamp_tmp, "%Y年%m月%d日%H:%MJST")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_14(self,bs4Obj):
        try:
            #BBC
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select("div.date.date--v2")[0].string, "%d %B %Y")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_15(self,bs4Obj):
        try:
            #Reuter
            bs4Obj = bs4Obj
            m1 = re.match(r'(January|February|March|April|May|June|July|August|September|October|November|December) \d{1,2}, \d{4}',str(bs4Obj.select(".ArticleHeader_date")[0].string))
            m2 = re.search(r'\d{1,2}:\d{1,2}',str(bs4Obj.select(".ArticleHeader_date")[0].string))
            news_timestamp = datetime.datetime.strptime(m1.group()+' '+m2.group(), "%B %d, %Y %H:%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_16(self,bs4Obj):
        try:
            #Wall Street Journal
            bs4Obj = bs4Obj
            m = re.sub(' ','',str(bs4Obj.select(".timestamp.article__timestamp")[0].string))
            m = re.sub('\n','',m)
            m = re.match(r'(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec).(\d{1,2}),(\d{4})(\d{1,2}):(\d{1,2})',str(m))
            tmp = m.groups()
            timesamp_tmp = tmp[0]+' '+ tmp[1].zfill(2)+' '+tmp[2]+' '+tmp[3].zfill(2)+' '+tmp[4].zfill(2)
            news_timestamp = datetime.datetime.strptime(timesamp_tmp, "%b %d %Y %H %M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_17(self,bs4Obj):
        try:
            #Forbes Japan
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select("time")[0].string, "%Y/%m/%d %H:%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_18(self,bs4Obj):
        try:
            #Newsweek
            bs4Obj = bs4Obj
            m = re.search(r'(\d{1,2})/(\d{1,2})/(\d{1,2}) at (\d{1,2}:\d{1,2}) ', str(bs4Obj.select('time')[0].string))
            tmp = m.groups()
            timesamp_tmp = tmp[0].zfill(2)+' '+ tmp[1].zfill(2)+' '+'20'+tmp[2].zfill(2)+' '+tmp[3]
            news_timestamp = datetime.datetime.strptime(timesamp_tmp, "%m %d %Y %H:%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_19(self,bs4Obj):
        try:
            #CNN.co.jp
            bs4Obj = bs4Obj
            m1 = re.search(r'\d{4}.\d{2}.\d{2}', str(bs4Obj.select("div .metadata-updatetime")[0]))
            m2 = re.search(r'\d{1,2}:\d{1,2}', str(bs4Obj.select("div .metadata-updatetime")[0]))
            news_timestamp = datetime.datetime.strptime(m1.group()+' '+m2.group(), "%Y.%m.%d %H:%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_20(self,bs4Obj):
        try:
            #BBC 2
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select("div.date.date--v2")[0].string, "%Y年%m月%d日")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_21(self,bs4Obj):
        try:
            #ABC News
            bs4Obj = bs4Obj
            tmp = re.match(r'(January|February|March|April|May|June|July|August|September|October|November|December) (\d{1,2}), (\d{4}), (\d{1,2}:\d{1,2}) (AM|PM)',bs4Obj.select(".Byline__Meta.Byline__Meta--publishDate")[0].string)
            hour = int(tmp.groups()[3].split(':')[0])
            mini = tmp.groups()[3].split(':')[1]
            if tmp.groups()[4] == 'PM':
                hour += 12
            hour = str(hour)
            news_timestamp = datetime.datetime.strptime(tmp.groups()[0]+' '+tmp.groups()[1]+' '+tmp.groups()[2]+' '+hour+' '+mini,"%B %d %Y %H %M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_22(self,bs4Obj):
        try:
            #外務省
            bs4Obj = bs4Obj
            j2w = jeraconv.J2W()
            m = bs4Obj.select('.rightalign')[0].string
            y =  m.split('年')[0]
            md = m.split('年')[1]
            news_timestamp = datetime.datetime.strptime(str(j2w.convert(str(y)+'年'))+'年'+ md, "%Y年%m月%d日")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_23(self,bs4Obj):
        try:
            #AFP BB
            bs4Obj = bs4Obj
            for meta_tag in bs4Obj.find_all('meta', attrs={'property':"article:modified_time"}):
                m = re.match(r'\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}',meta_tag.get('content'))
                news_timestamp = datetime.datetime.strptime(m.group(),"%Y-%m-%dT%H:%M:%S")
                return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_24(self,bs4Obj):
        try:
            #NHK News
            bs4Obj = bs4Obj
            for meta_tag in bs4Obj.find_all('time'):
                news_timestamp = datetime.datetime.strptime(meta_tag.get('datetime'),'%Y-%m-%dT%H:%M')
                return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_25(self,bs4Obj):
        try:
            #日経新聞 株
            bs4Obj = bs4Obj
            m = re.search(r'\d{4}/\d{1,2}/\d{1,2} \d{1,2}:\d{1,2}',bs4Obj.select('.cmnc-publish')[0].string)
            news_timestamp = datetime.datetime.strptime(m.group(), "%Y/%m/%d %H:%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_26(self,bs4Obj):
        try:
            #日刊工業新聞
            bs4Obj = bs4Obj
            m = re.search(r'\d{4}/\d{1,2}/\d{1,2} \d{2}:\d{1,2}',str(bs4Obj.select('.date')[1]))
            news_timestamp = datetime.datetime.strptime(m.group(), "%Y/%m/%d %H:%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_27(self,bs4Obj):
        try:
            #朝日新聞　論座
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select('.date')[0].string, "%Y年%m月%d日")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_28(self,bs4Obj):
        try:  
            #朝日新聞　中高生新聞
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select('.date')[0].string, "%Y年%m月%d日")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_28(self,bs4Obj):
        try:  
            #EUROPA NEWSWIRE
            bs4Obj = bs4Obj          
            m = re.search(r'(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec) (\d{1,2}), (\d{4})',bs4Obj.select(".icon-cal")[0].string)
            news_timestamp = datetime.datetime.strptime(''.join(m.groups()), "%b%d%Y")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_29(self,bs4Obj):
        try:
            #国連広報センター
            bs4Obj = bs4Obj
            news_timestamp = datetime.datetime.strptime(bs4Obj.select("#cm_header_text")[0].string, "%Y年%m月%d日")
            return news_timestamp
        except Exception as e:
            return None    

    def scrape_return_timestamp_29(self,bs4Obj):
        try:
            #OPCW News
            bs4Obj = bs4Obj 
            m = re.search(r'(\d{1,2}) (January|February|March|April|May|June|July|August|September|October|November|December) \d{4}',bs4Obj.select(".news__date")[0].get_text())
            news_timestamp = datetime.datetime.strptime(m.group(), "%d %B %Y")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_30(self,bs4Obj):
        try:
            #HAARETZ
            bs4Obj = bs4Obj
            m = re.search(r'(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec) \d{1,2}, \d{4} \d{1,2}:\d{1,2}',bs4Obj.select("time")[1].get_text())
            news_timestamp = datetime.datetime.strptime(m.group(), "%b %d, %Y %H:%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_31(self,bs4Obj):
        try:
            #THE DAILY STAR
            bs4Obj = bs4Obj
            m = re.match(r'(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec). (\d{1,2}), (\d{4}) \| (\d{1,2}):(\d{1,2})',bs4Obj.select("time")[0].get_text())
            news_timestamp = datetime.datetime.strptime(''.join(m.groups()), "%b%d%Y%H%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_32(self,bs4Obj):
        try:
            #INDEPENDENT
            bs4Obj = bs4Obj
            m = re.search(r'\d{4}-\d{1,2}-\d{1,2}T\d{1,2}:\d{1,2}',str(bs4Obj.select("amp-timeago")[0]))
            news_timestamp = datetime.datetime.strptime(m.group(), "%Y-%m-%dT%H:%M")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_33(self,bs4Obj):
        try:
            #ジェトロ
            bs4Obj = bs4Obj
            m = re.search(r'\d{4}年\d{1,2}月\d{1,2}日',str(bs4Obj.select('p')))
            news_timestamp = datetime.datetime.strptime(m.group(), "%Y年%m月%d日")
            return news_timestamp
        except Exception as e:
            return None

    def scrape_return_timestamp_34(self,bs4Obj):
        try:
            #夕刊フジ
            bs4Obj = bs4Obj 
            m = re.search(r'\d{4}.\d{1,2}.\d{1,2}',str(bs4Obj.select('#__r_publish_date__')[0]))
            news_timestamp = datetime.datetime.strptime(m.group(), "%Y.%m.%d")
            return news_timestamp
        except Exception as e:
            return None


    def main(self,URL):
        self.URL = URL
        try:
            get_url_info = requests.get(URL,headers=self.headers)
            bs4Obj = bs4.BeautifulSoup(get_url_info.content, 'lxml')
        except Exception as e:
            print(e)
            return 'URLにアクセスできません'

        for i in range(1,35):
            func_name = 'self.scrape_return_timestamp_' + str(i)
            ts_temp = eval(func_name)(bs4Obj)
            if ts_temp:
                return td_temp

test.py

from news_timestamp import *

TS = ScrapeNewsTimestamp()
news_timestamp = TS.main('https://www.mofa.go.jp/mofaj/press/release/press1_000423.html')
print(news_timestamp)

2020-02-15 00:00:00

こちらにも置いておきます。
https://github.com/KanikaniYou/news_timestamp