两日期间隔周数计算器
输入两个日期，即时计算它们之间的精确周数，包括完整周数、剩余天数、总天数和小数周数。适用于孕期追踪、项目规划、学期安排等场景。
Common Scenarios
Click a scenario to set the end date relative to the start date (or today).
Frequently Asked Questions
两个日期之间的周数是如何计算的？
两日期间的周数 = 天数差 / 7。计算器先计算两个日期之间的总天数（包含或不含起止日，可选），然后除以 7 得到完整周数，余数以天数显示。结果可以是整数或含小数的精确数值。
如何计算距离某个重要日期还有几周？
输入今天和目标日期，计算器会显示剩余周数和天数。例如，距离婚礼/考试/假期还有多少周可以直观掌握准备时间。你也可以查看某个过去的事件发生了多少周前。
孕期周数如何计算？
孕期以末次月经（LMP）第一天为起点计算，整个孕期约 40 周（280 天）。输入末次月经日期，本计算器可计算当前孕周数和预产期。孕周通常以"X 周 Y 天"格式表示（如 28 周 3 天）。
如何计算某人的年龄（以周数表示）？
输入出生日期，计算器会显示从出生到今天的完整周数。对于婴儿和新生儿，周龄是医生监测发育的重要指标（如 8 周体检、12 周里程碑等）。成人年龄也可以用周数表达，约 1 年 = 52.18 周。
How to Count Weeks Between Two Dates
To count the number of weeks between two dates, find the total number of days separating them and divide by 7. The whole number part gives you complete weeks; the remainder gives extra days. For example, 45 days equals 6 full weeks and 3 remaining days (6 weeks + 3 days).
Formula
Total Days = |Date2 − Date1| in milliseconds ÷ 86,400,000
Full Weeks = Math.floor(Total Days ÷ 7)
Remaining Days = Total Days mod 7
Decimal Weeks = Total Days ÷ 7
The absolute difference ensures the result is always positive, regardless of which date is entered as start or end. The total days are divided by 86,400,000 (the number of milliseconds in one day) and rounded to handle daylight saving time transitions.
Common Week Counts
| Duration | Weeks | Total Days |
|---|---|---|
| 1 month | ~4.3 weeks | 28–31 |
| Quarter (3 months) | 13 weeks | 91 |
| College semester | 15–16 weeks | 105–112 |
| Half year | 26 weeks | 182–183 |
| Full year | 52 weeks | 365–366 |
| 2 years | 104 weeks | 730–731 |
Pregnancy Weeks
A full-term pregnancy lasts approximately 40 weeks (280 days) from the last menstrual period (LMP). Doctors track pregnancy in weeks because fetal development milestones are tied to gestational age in weeks. Each trimester covers roughly 13 weeks:
| Trimester | Weeks | Days |
|---|---|---|
| First trimester | Weeks 1–13 | Days 1–91 |
| Second trimester | Weeks 14–27 | Days 92–189 |
| Third trimester | Weeks 28–40 | Days 190–280 |
To use this calculator for pregnancy: enter your LMP date as the start date and today's date (or your due date) as the end date. The result shows exactly how many weeks pregnant you are and the remaining days within the current week.
Project Planning with Weeks
Weeks are a natural unit for project planning. Sprints in agile development are typically 1–4 weeks; school semesters run 15–16 weeks; fiscal quarters span 13 weeks. Use this calculator to:
- Determine how many sprints fit between a project start and a release date
- Calculate how many weeks remain until a deadline
- Convert a contract duration (e.g., 90 days) into weeks for scheduling
- Find the end date for a fixed-week engagement (use the scenario buttons)
Examples
How many weeks from January 1, 2026 to March 1, 2026?
January has 31 days and February 2026 has 28 days (not a leap year), giving 59 total days. 59 ÷ 7 = 8 full weeks with 3 remaining days (8 weeks, 3 days).
How many weeks are in a school year?
A typical US school year runs from early September to mid-June, roughly 36 weeks (180 instructional days). From September 2 to June 5 is approximately 276 days = 39 weeks and 3 days.
Related Tools
- Date Calculator — Find days between dates or add/subtract days from a date
- Date Add/Subtract Calculator — Add or subtract weeks, months, and years from any date
- Business Days Calculator — Count working days between two dates, excluding weekends
- Age Calculator — Calculate exact age in years, months, and days