Question: The city of Gavle received its charter during which era?
Context: M.E.T.S. Charter School (formally known Mathematics, Engineering, Technology, & Science Charter School) is a seven-year comprehensive public charter middle school / high school that serves students in sixth through twelfth grades in Hudson County and Essex County of New Jersey, United States.  The M.E.T.S. Charter School has two campuses, one in Jersey City and one in Newark.  The school operates under the terms of a charter granted by the New Jersey Department of Education.  M.E.T.S. Charter School is an Early College Preparatory School that utilizes research-based instructional practices to achieve student proficiency in mathematics, engineering, technology, and science.  The school is committed to providing a high quality education focused on college and career readiness while fostering an equitable, innovative, and creative learning environment.  M.E.T.S. Charter School encourages all students to take college level courses and graduate from high school within four years with up to 60 college credits and/or an associate degree.  Postsecondary success is promoted by prioritizing admission to a four-year college or university for each member of our graduating class. Yuba City Charter School is a K-12 public school located in Yuba City, California.  Yuba City Charter School is a college prep and CTE program that models and supports the development of good character while emphasizing rigorous academics and career preparation.  The school is a student centered direct instruction model, and offers a student success program to help struggling students improve performance, skills, and credit recovery.  All students K-6 receive daily formal instruction in music, PE, and Spanish language.  Yuba City Charter is fully accredited by the Western Association of Schools and Colleges (WASC).  All core high school classes meet the University of California A-G requirements for admission to UC.  The student-teacher ratio for K-3 is 20:1 In grades 4-6, classes are capped at 25.  In grades 7-12, classes are capped at 28.  These caps have been established to ensure small class sizes and to facilitate significantly greater individualized instruction than is available in other schools.  Yuba City Charter School also encourages community service and parent participation.  YCCS has established a Parent Advisory Committee, and encourages all parents to join.  Yuba City Charter School is a public charter school.  Enrollment is open to all students without exception.  The school is located at 256 Wilbur Ave. in Yuba City, near the Sutter County Fair Grounds.  Yuba City Charter School strives for high academic achievement in a small-school atmosphere.  YCCS believes that the small school environment paired with individualized instruction and service provides the best educational experience for all students. In the United States, a charter city is a city in which the governing system is defined by the city's own charter document rather than by state, provincial, regional or national laws.  In states where city charters are allowed by law, a city can adopt or modify its organizing charter by decision of its administration by the way established in the charter.  These cities may be administered predominantly by residents or through a third-party management structure, because a charter gives a city the flexibility to choose novel types of government structure.  Charter cities are similar in administrative structure to special administrative regions. Crescent City Schools is a Charter Management Organization (CMO) based in New Orleans, Louisiana and founded by educators Kate Mehok and Julie Lause.  Both were honored by the New Schools Venture Fund in 2013 as Entrepreneurs to Watch for their contributions to public education.  Crescent City Schools is part of a movement in New Orleans to transform one of the worst school systems in the country.  In the fall of 2010, Crescent City Schools received a Type 5 charter from the state of Louisiana to transform a failing school in New Orleans.  In February 2011, Crescent City Schools was assigned to Harriet Tubman, a K-8 school in Orleans Parish, and assumed operations there on July 1, 2011.  In 2012, the organization was awarded the expanded charter for Akili Academy of New Orleans and the charter for Paul B. Habans Elementary.  Habans opened as Paul Habans Charter School in July 2013. Christopher of Bavaria (26 February 1416 – 5/6 January 1448) was King of Denmark (1440–48, as Christopher III), Sweden (1441–48) and Norway (1442–48) during the era of the Kalmar Union. The Pennsylvania Virtual Charter School (PAVCS) is a public virtual charter school.  Pennsylvania Virtual Charter School is headquartered at 630 Park Avenue, King of Prussia, Pennsylvania, US 19406.  In 2015, enrollment was reported as 2,482 pupils in kindergarten through 12th grades, with 56.7% of pupils eligible for a free lunch due to the family meeting the federal poverty level.  Additionally, 16% of pupils received special education services, while none of the pupils were identified as gifted.  The school employed 104 teachers.  Per the Pennsylvania Department of Education, 100% of the teachers were rated "Highly Qualified" under the federal No Child Left Behind Act.  Cyber charter schools enroll many homeschooled students and also children with special needs, who are taught remotely via computer.  The school is one of the 14 public, cyber charter schools operating in Pennsylvania in 2015.  PA Virtual Charter School is a federally designated Title I school. Euralair was a charter airline based in France.  Euralair was founded in 1964 as an air-taxi and executive charter company.  In 1966 it became charter airline and operated its first charter flights in 1968 when it received the first Fokker F-27 (F-BRHL) on November 11, 1968 and the second (F-BRQL) on October 15, 1969; the last one sold to the Swiss company Belair (as HB-AAZ) in June 1973.  In order to develop its charter activity, on November 1971 Euralair bought from Austrian Airline the first Sud Aviation Caravelle VIR (F-BSEL) and in 1973 the second (F-BTDL). The Dongan Charter is the 1686 document incorporating Albany, New York as a city.  Albany's charter was issued by Governor Thomas Dongan of the Province of New York, a few months after Governor Dongan issued a similarly worded, but less detailed charter for the city of New York.  The city of Albany was created three years after Albany County.  The charter is the oldest existing city charter still in force in the United States and "arguably in all the Western Hemisphere", according to Stefan Bielinski, former senior historian of the New York State Museum.  In 1936 the United States Congress commemorated the charter's 250th anniversary by minting a half dollar coin. Gävle ] is a city in Sweden, the seat of Gävle Municipality and the capital of Gävleborg County.  It had 99,576 inhabitants in September 2016, which makes it the 13th most populated city in Sweden.  It is the oldest city in the historical Norrland (Sweden's Northern Lands), having received its charter in 1446 from Christopher of Bavaria.  However, Gävle is far nearer the greater Stockholm region than it is to the other major settlements in Norrland. Boston Renaissance Charter Public School (BRCPS), formerly Boston Renaissance Charter School (BRCS), is a charter elementary school in the Hyde Park area of Boston.  It is one of the oldest charter schools in Boston, and as of 2012 BRCPS was also one of the largest charter schools in the city.  In 2001 it was the largest American charter school that operated out of a single campus, and in 2005 it was the largest charter school in the state of Massachusetts.  Overall it was one of the largest charter schools in the United States.  It formerly served middle school grades but now only serves elementary school.
Answer: era of the Kalmar Union