Magic Hat: They use a production date. Ex.: M051. M= December (A=January, B=Feb, etc. I is skipped, so J=September, etc.), 05= 5th day, 1= 2011. Recommended shelf life 120 days from that date.

Maine Beer: They use a bottling date which is clearly written on the back label, ex: 072912.

Mankota: They use a drink by date. Bottles are date stamped and shelf life is 120 days.

Mammoth: They use a bottling date. From information we have seen the brewer states that they currently don't do a date on the bottle, but do have a date on the outside of the case. From that date, they guarantee the quality for three months. Format is MM/DD/YY.

Manzanita: They use bottling date on their cases only.

Marble (MA): They use a bottling date which is located right next to the government warning.

Marin: They use a bottling date which is located on the outside of the cases only.

Maritime Pacific: They use a best before date which is stamped only on the outside of the cases boxes. Bottling date is 3 months before. Format is MM/DD/YYYY.

Marshall (OK): They use a bottling date that is date is stamped on the case only.

Matt Brewing: They use a 4 digit bottling date. First 3 digits are for the day of the year and the last digit is the year. So 0218 was bottled on 21st day of 2008 or January 21, 2008.

Maui Brewing: They use a bottling date. The cans are inked with the date on the bottom margin. Format is MM/DD/YYYY.

Mayflower: They use a packaged on date which is stamped on the labels. Format is DD/MM/YY.

McKenzie: They use bottle numbers. Only bottles in small quantities.

McMenamins: They use a packaging date. On the box case only.

Mendocino: They use a packaging date which is on the cases only in a format for internal use.

Mercury: They use a bottled on date which is stamped on the bottle, format MM/DD/YY.

Metropolitan: They use a best before date. It's on the bottom of the packaging of the six-packs. Format is DD/MM/YY. The date is 5 months from bottling.

Midnight Sun: They use a packaged on date. Format is: JUN 09 2013. For the year-round & seasonal brews, the month (JFMAMJJASOND) and week (12345) are notched on the side of the label.

Miller: They use a pull code on the side of bottles, kegs, and cartons, and on the bottom of cans. Miller codes contain two lines. The first line indicates the date: "01 01 9" indicates that the beer should no longer be available for sale on January 1, 2009. The second line of digits represents brewery production information. In this example, "A 1 52 84" signifies the Production Day: A, Brewery: 1, Line: 52, and Time: 84.

Millstream: They use a bottling date. From information we have seen the brewer states that their bottles have the bottling date on the label.  If you look on the side (usually right) it will have a little notch for what month it was bottled in.  For example J would be January, F would be February, etc.   Then across the top of the label you have to pretend it has the 30 days in the month up there.  To the left side would be the 1st of the month, towards the middle of the label would be around the 15th and to the right of the label would be the 30th of the month.

Milwaukee Ale House/Brewing: They use a bottling date. From information we have seen the brewer states that the bottles are coded on bottling date.  It is actually coded label cuts on the right side of body label. They generally want the beer consumed within 90 days.

Minhas: They use a best before production date.The can or bottle code is the Julian date of production plus one year. So, say today's date: 173 10 15 would be the 173rd day of 2010. The 15 refers to the 15th hour of the day. Shelf life is 1 year.

Moat Mountain: They use a canning date for cans and a bottling date on their bombers, only on the master cases for now.

Mogollon: They use a packaging date which is only stamped on the cardboard flat of the cases. Format should be DD/MMM/YYYY. Shelf-life is 6 months.

Molson: They use a 13-character bottling code beginning with a letter and three digits. The letter is the month, the first two digits are the day and the last digit is the year. Thus E169 is May 16, 1999.

Monday Night: They use a best before date located on the case box only.

Mother Earth Brew (CA): They use a bottling date which is stamped on the cases only.

Mother Earth Brewing: They use a bottling date. All bottles have a MM/DD//YY date on the label.

Mother's Brewing: They use a packaged date. It's a standard day/month/year.

Motor City: They use a bottling date. From information we have seen the brewer states that there is a date stamp which reflects the day the beer was bottled.  However, this stamp is on the case carrier and not the bottle.The month is spelled out then day and year.

Mount Pleasant: They use a bottling date which is a Julian date code. On the upper right hand side of the label is an 8 digit number. First 3 digits are the day of the year, next 2 is the year and the last 3 are the batch number.

Moylan's: They use a bottling date which is on the cases. Format is MM/DD/YYYY.

Mystic: They use a batch number. Some of the batch info is on the website but you can always email the brewer for more specifics.