In general, a gap in coverage that lasts less than three months qualifies as a short coverage gap and not subject to a penalty. If you have more than one short coverage gap during a year, the short coverage gap exemption only applies to the first gap. If you have a coverage gap of 3 months or more, you are not exempt for any of those months.
If you do not have coverage for a continuous period that begins in one taxable year and ends in the next, for purposes of applying the short coverage gap rules to the first taxable year, the months in the second taxable year included in the continuous period are not counted. For purposes of applying the short coverage gap rules to the second year, the months in the first taxable year are counted.
For example, if you lacked coverage from November 1, 2018 until February 1, 2019, November and December of 2018 are treated as a short coverage gap on your 2019 tax return. On your 2019 return, however, November and December of 2015 are included in the continuous period that includes January 2019. That continuous period is not less than 3 months so, on your 2019 return, January of 2019 is not an exempt month under the short coverage gap exemption.