Units of Time

Need to know how to refer to a particular unit of time? Here are some of the most common ones in Spanish, listed from the shortest period of time to the longest:

• el nanosegundo — nanosecond
• el microsegundo — microsecond
• el milisegundo — millisecond
• el segundo — second
• el minuto — minute
• la hora — hour
• el día — day
• la semana, el septenario — week
• la quincena — fortnight, two weeks (The Spanish term sometimes refers to a 15-day period or a half-month.)
• el mes — month
• el semestre — six months, half-year (The Spanish term can also refer to an academic semester.)
• el año — year
• el lustro — five years
• el decenio, la década — 10 years, decade
• el siglo — century
• el milenio — millennium
• el cron — million years
• el eón — thousand million years, billion years in U.S. English (The Spanish term also can refer to an indefinitely long period of time.)

In addition, Spanish has a number of units of time that are seldom used, or are used in specific contexts. For example, bimestre and trimestre, are two-month and three-month periods, respectively, with similar month groupings possible. Similarly, bienio and septenio are two- and seven-year perdiods of time, respectively, with other groupings possible.