Ah, a Zombie Apocalypse.

The government has a plan of action, called CONOP 8888, should one ever happen. There are three stages:

Stage 1:

Make and maintain a defensive position.

Find all the areas that zombies are most likely to come up in and tackle them first, through the military. Then 'deal with all the conditions known to be conductive in the creation of new threats.' In other words, tackle all the factors that make new threats; for example giving sufficient food and water to people so they don't start rioting, therefore making more trouble. 

Stage 2:

Eliminate the threat.

After making a defensive move, the government will take up an attacking stance and start making new drugs and vaccines to combat infection.

Stage 3:

Get back to normal.

Normal services will start returning and whilst it won't be the same, shops, schools and a stable economy will start returning.

What will probably happen:

Say it happens on the 1st of January.

Jan 1: the first zombie is taken to a secure location, but not before its bitten a few people.

Jan 4: more and more zombies start getting out, and more people start getting infected. This is because they do not realise that it's not the same person anymore, and instead try making big speeches and get bitten half way through.

Jan 8: people start panic-buying.

Jan 17: shops are almost fully out of supplies.

Jan 28: people have started barricading themselves in their home.

Feb 2: the government start handing out leaflets on how to combat the zombies.

Feb 8: the first mass-shooting of zombies.

Feb 19: vast majority of people have barricaded themselves.

Feb 28: sixteen people are killed in a crush at a shop entrance.

Mar 4: the first few shady supplies are out, claiming that they kill zombies instantly or cure you fully of infection. Very shady, but a lot of people are desperate enough to buy it.

Mar 21: Antartica and Australia are the only uninfected ones. People flock to it, bringing infection.

Mar 29: almost every single country has gone into full lockdown to prevent infection.

Jun 3: after almost nothing happening for a month, the government announces a breakthrough in a vaccine. Hundreds of thousands of people lie about who they are to get a jab, resulting in vulnerable people being mistakenly exposed to zombies and the people with vaccines stay at home, since the government think they're vulnerable.

Jun 13: almost every single abandoned home has been raided.

Jun 28: huge peak in zombie infection rates.

July 17: zombie infection rates go down, and because if this people think it's safe to go outdoors. Thus, more infections. The only people alive by this point are the sensible ones.

Sep 2: zombies are being captured and held in secure bases, should it be able to turn back into a normal person.

Sep 19: people are keeping zombified loved ones in sheds, bathrooms, and cupboards, rather than hand them over.

Oct 7: it starts to go down, as the ones stupid enough to go outdoors have been killed. The ones that have planned ahead are fine.

Oct 31: the black market is going down supremely. People that have been thinking they're safe because they bought shady cures are now infected, and there are no buyers left.

Nov 1: almost every household has a radio, and are listening to updates.

Nov 12: the sensible people get vaccines, and herd immunity is established.

Nov 17: the army are taking in volunteers and almost all the zombies have been captured; the ones in cupboards and sheds have been taken in.

Nov 34: most people have lost track of the date.

Dec 12: normal starts to return, and since there are only sensible people left in the world, progress and development soars.

Dec 18: you wake up from your dream and realise that it's fine. Zombies were never real, you're safe in your bed and you can smell pancakes.