I've read a research paper on this and that the conclusion was that the best time to post is on monday during lunch hour.
Statistics wise they say it's about a 5% increase in active user base over the average mark. Worst time is on friday night I believe with a 2% drop in active readers.
Do note that these are for Articles and not web novel chapters so I don't know how it fares over here.
There is also this website article where researchers poll the engagement for various social media websites. I thought it might be relevant so I'm just going to post it here.
When will your posts get the most traction? New data from Sprout Social shows when most people are engaging with social media platforms.
www.impactbnd.com
Data seems to conclude that best time to post is during the weekdays between lunch and in the evening. Data also concludes that weekends are often the time with the least viewer engagement.
Of course SH is a international website. But I assumed the data could be mapped to bigger audience, so weekdays are probably your best bet. Monday's or Wednesday's.
Do take this info with a grain of salt. My word is not absolute.