Which one is correct?
"for 4 days" or "since 4 days"?

Some examples from the web:

• Dogs should not be allowed to swim in surface waters for 4 days after treatment.
• You've been gone for 4 days.
• Fajngold's been gone for 4 days now.
• They've been holed up in there for 4 days now but it went unnoticed because of the holiday weekend.
• He kept michelle for 4 days.
• I'll keep her going for 4 days and 3 nights.
• The time independent pharmacokinetic profile of levetiracetam was also confirmed following 1500 mg intravenous infusion for 4 days with b. i. d dosing.
• Dogs should not be allowed to swim in ditches, ponds or streams for 4 days after treatment.
• Here, 40,000 fans descend on a small town in Germany for 4 days of beer, partying and heavy metal.
• Multiple dose administration of 200 mg thalidomide q. d. for 4 days had no effect on the international normalized ratio (INR) in healthy volunteers.
• Itraconazole, a potent CYP3A4 inhibitor, at 200 mg/ day orally for 4 days had no significant effect on the pharmacokinetics of intravenous fentanyl.
• I've been eating dust for 4 days!
• Water has been coming out for 4 days!
• Persistent allergic rhinitis is defined as the presence of symptoms for 4 days or more per week and for more than 4 weeks.
• If your allergic rhinitis is persistent (presence of symptoms for 4 days or more per week and for more than 4 weeks), your physician may recommend you a longer term treatment.
• Fifteen yearold girl, with a new baby, you felt comfortable letting her stay with a friend for 4 days?
• How can you wear the same clothes for 4 days and sit near my daughter smelling like that?
• This will mean that you wear one patch for 3 days and the other for 4 days.
• In persistent allergic rhinitis (presence of symptoms for 4 days or more per week and for more than 4 weeks), continued treatment may be proposed to the patients during the allergen exposure periods.
• Mixing of the soil constituents; distributing the soil to the test vessels; incubation at test conditions for 4 days;

Some examples from the web:

• It's been 4 days since Bonnie died - or 4 days since I found out Bonnie died.
• It's been 4 days since the incident.
• It's been 4 days since my wingman went.
• It's been 4 days since she... disappeared following her shift at a local restaurant.
• Since there are 4 more days of travel.
• Since its 4 nights 5 days, we can't really go on a long vacation...
• Because in 4 days, it'll be 10 years since J-Stryke was murdered.
• Median time to normocalcaemia was 4 days.
• In general this disappears within 4 days.
• The connection to the submarine ended 4 days ago.
• It takes about 4 days by EMS.
• I've been up since 4 a.m.
• It had gotten a lot better since 4 a.m.
• Been up since 4:00.
• There is nothing new since 4 am.
• There has been nothing new since 4 a.m.
• We're celebrating 90210, the greatest zip code since 4...
• I've been outside your door since 4:30.
• I believe that we have made considerable progress since 4 February.
• 4-day workweeks, free drinks - Livin' the dream.