上旬

1. Origins, structure, and basic meaning

• Structure: 上旬 (じょうじゅん) means approximately the first ten days of a month. Both examples use 上旬に after a month expression.
• Basic usage: Results are scheduled for mailing early next month; cherry blossoms began opening in early April.

2. Common pitfalls and similar expressions

• Scheduled mailing window and onset of a seasonal event
  • 来月上旬 is a relative future period; 四月の上旬 is a calendar-defined past period. Neither specifies one exact day.