Per the Maryland Taxes website:
The second Sunday of August to the following Saturday is designated as Shop Maryland Tax-Free Week each year. That means qualifying apparel and footwear $100 or less, per item, are exempt from the state sales tax. Beginning in 2017, the first $40 of a backpack or bookbag purchase is also tax-free. Accessory items, except for backpacks, are not included. The Shop Maryland Tax-Free Week for 2018 is Sunday, August 12 - Saturday, August 18.
Additionally, there is a tax-free three-day weekend every February during which the state sales tax will not apply to the sale of any Energy Star Product listed below, or solar water heater. The Shop Maryland Energy Tax-Free weekend for 2018 is February 17 - 19.
Energy Star Product means an air conditioner, clothes washer or dryer, furnace, heat pump, standard size refrigerator, compact fluorescent light bulb, dehumidifier, or programmable thermostat that has been designated as meeting or exceeding the applicable Energy Star Efficiency requirements developed by the U.S. Environmental Protection Ag