Basic Points

• DTE stands for "days to expiration" and is how many calendar days are remaining until the contract expires. This pertains both to futures and options. 
• DTE is a core point of mechanics for any options strategy, as dynamics change substantially based on differences in DTE. 
• An option’s value decays faster when DTE is lower.
• An option’s value is less sensitive to changes in implied volatility when DTE is lower. 
• Short options are riskier when DTE is lower.

Advanced Discussion

When we look at term structure edge with different DTEs, we want an advantage by writing on a date with a higher IV% and buying on a date with a lower IV%. But sometimes there are seasonal reasons why IV should be higher or lower in different months, which complicates this analysis.

Another term commonly used as a unit of DTE is tenor. When we say “first tenor” we mean the first (shortest-duration) month, the second tenor is the second month out, the third tenor is the third month out, and so on. This means that the first tenor is the front month and the second tenor is the back month.