⏰ Lesson 3.2: Time, Schedules & Conversions

Time Runs Care

Think about a single day on a care unit. A CNA arrives for a shift, reads the assignment board, helps residents through the morning, takes and records measurements at set times, and then hands off to the next shift. Families visit on a schedule. Meals, rest, and activities happen at set hours. All of it is held together by time — and when care runs 24 hours a day, getting the time right really matters.

That's why this lesson treats time as a skill, not a guessing game. You'll learn to read the 24-hour clock confidently (so "3 o'clock" is never ambiguous), to work out when your shift ends and how many hours it was, and to convert between common units with a method you can trust. These are the same everyday math moves from Math & Numeracy and Lesson 3.1, now put to work in the rhythm of healthcare. None of it is medication math — it's the ordinary, useful time-and-measurement math that keeps a caring day on track.

If numbers make you nervous, you are in very good company — and you are in the right place. Take the examples one small step at a time, and check each answer the way we'll practice. Steady beats fast.

The 24-Hour (Military) Clock

Healthcare settings often use the 24-hour clock (sometimes called military time) for charting and schedules. Why? Because it removes AM/PM confusion. "7:00" could be morning or evening; 07:00 and 19:00 can never be mixed up. When records are about people's care, that clarity is worth it.

How it works

The 24-hour clock runs from 00:00 (midnight) to 23:59 (one minute before the next midnight). It uses four digits: the first two are the hour (00–23), the last two are the minutes (00–59). Two simple rules cover almost everything:

• Before noon (AM): the hour is the same — just write it with two digits. 9:00 AM = 09:00, 7:45 AM = 07:45.
• After noon (PM): add 12 to the hour. 1:00 PM → 1 + 12 = 13:00, and 3:30 PM → 3 + 12 = 15:30.

Two special cases to memorize: midnight = 00:00 (sometimes written 24:00 at the very end of a day) and noon = 12:00 (12 PM stays 12 — you don't add 12 to it). To go the other way, from 24-hour back to AM/PM: if the hour is 13 or higher, subtract 12 and add "PM" (so 20:30 → 20 − 12 = 8:30 PM); if it's 00, that's 12 midnight; hours 01–11 are just AM; and 12 is noon.

A conversion table you can trust

Here are common conversions, each one checked. Read across, and try covering the right column and predicting each answer:

Notice the minutes never change — only the hour does. "Add 12 for PM, keep the same for AM, and remember midnight = 00:00 and noon = 12:00" will carry you through nearly every case.

Shifts & Schedules

Because care never stops, healthcare jobs are built around shifts. Two of the most common lengths are 8-hour shifts (often three of them cover a day) and 12-hour shifts (often two cover a day). You'll want to answer three everyday questions with confidence: When does my shift end? How long was it? How many hours did I work this week?

Question 1: When does the shift end? (add the length to the start)

Start with the start time on the 24-hour clock and add the shift length. If the total goes past 24, subtract 24 to roll into the next day.

• Example: A shift starts at 07:00 and lasts 8 hours. 7 + 8 = 15, so it ends at 15:00 (3:00 PM). ✔
• Example (rolls past midnight): A night shift starts at 19:00 and lasts 12 hours. 19 + 12 = 31; since 31 is past 24, subtract: 31 − 24 = 7, so it ends at 07:00 the next morning. ✔
• Example: A night shift starts at 23:00 and lasts 8 hours. 23 + 8 = 31; 31 − 24 = 7, so it ends at 07:00 the next morning. ✔

Question 2: How long was the shift? (elapsed time = end − start)

When both times are on the same day, subtract the start from the end.

• Example: A shift runs 07:00 to 15:00. 15 − 7 = 8 hours. ✔
• Example: A shift runs 15:00 to 23:00. 23 − 15 = 8 hours. ✔
• Example: A shift runs 07:00 to 19:00. 19 − 7 = 12 hours. ✔

If a shift crosses midnight, a simple trick is to count to midnight, then add the rest. For a 23:00 to 07:00 shift: from 23:00 to midnight is 1 hour, and from 00:00 to 07:00 is 7 hours, so 1 + 7 = 8 hours total. ✔

Question 3: How many hours this week? (add up the shifts)

Once you know each shift's length, a weekly total is just addition.

• Example: Three 12-hour shifts in a week: 12 + 12 + 12 = 36 hours. ✔
• Example: Five 8-hour shifts in a week: 8 × 5 = 40 hours. ✔
• Example (mixed): Two 8-hour shifts plus one 12-hour shift: (8 + 8) + 12 = 16 + 12 = 28 hours. ✔

Reading a rotation

A schedule (or rotation) is just a table of who works when. Read across a row to see one person's week. Here's a small sample for one CNA:

This week is three 12-hour shifts: 12 + 12 + 12 = 36 hours. ✔ Reading a schedule well means you show up at the right time — a piece of the reliability and punctuality we'll cover in Lesson 4.1 (Professionalism & Ethics in Care).

Unit Conversions

A conversion means expressing the same amount in a different unit — the same weight in pounds or kilograms, the same volume in ounces or milliliters, the same span of time in hours or minutes. The amount doesn't change; only the unit does. A calm, reliable method makes these easy, and it's the same every time:

graph TD
    A["Identify the units (from → to)"] --> B["Find the conversion factor"]
    B --> C{"Bigger unit to smaller,<br/>or smaller to bigger?"}
    C -->|"to smaller unit"| D["Multiply"]
    C -->|"to bigger unit"| E["Divide"]
    D --> F["Label the answer with its unit"]
    E --> F
    F --> G["Check: does the size make sense?"]

The last two steps matter as much as the math: always label the answer (a bare "68" means nothing — "68 kg" does), and always ask whether the size makes sense (a person's weight in kilograms should be a smaller number than in pounds, because a kilogram is a bigger unit).

Pounds and kilograms (concept)

A useful approximate factor is 1 kg ≈ 2.2 lb. Because a kilogram is bigger than a pound, a weight in kilograms is a smaller number, so to go from pounds to kilograms you divide by 2.2.

• Example: 150 lb ÷ 2.2 ≈ 68 kg (150 ÷ 2.2 = 68.18…, which rounds to about 68). ✔
• Example (clean): 220 lb ÷ 2.2 = 100 kg exactly (because 100 × 2.2 = 220). ✔

Ounces and milliliters (concept)

For liquid volume, a common approximate factor is 1 oz ≈ 30 mL. Because a milliliter is smaller than an ounce, a volume in milliliters is a bigger number, so to go from ounces to milliliters you multiply by 30.

• Example: 8 oz × 30 = 240 mL. ✔
• Example: 4 oz × 30 = 120 mL. ✔

Hours and minutes

The factor is exact: 1 hour = 60 minutes. Hours to minutes: multiply by 60. Minutes to hours: divide by 60.

• Example: 3 hours × 60 = 180 minutes. ✔
• Example: 2 hours 30 minutes = (2 × 60) + 30 = 120 + 30 = 150 minutes. ✔
• Example: 90 minutes ÷ 60 = 1.5 hours (one and a half hours). ✔

Managing Your Time

Put it all together and time math becomes a quiet professional strength. A reliable caregiver reads the 24-hour clock without hesitation, knows when their shift starts and ends, shows up on time, and double-checks any conversion before trusting it. None of this requires being "a math person" — it requires a calm method and a habit of checking.

These habits connect straight to Workforce Readiness (dependability is one of the first things employers look for) and to the professionalism thread running through this whole bridge. Being good with time is one of the most visible ways to show you can be counted on.

🔊 Hear It & Read Along — Key Sentences

Press 🔊 Listen on a sentence and follow the words with your eyes. Hearing and seeing a sentence at the same time builds reading fluency and confidence. Play each one as many times as you like.

Practice & Project

Tips & Common Mix-Ups

✅ Do's

• Add 12 for PM, keep the hour for AM. And remember midnight = 00:00, noon = 12:00.
• Subtract 24 when a shift crosses midnight. 19:00 + 12 = 31 → 31 − 24 = 07:00 next day.
• Use the conversion method every time. Identify units → find the factor → multiply or divide → label → check.
• Label every answer with its unit. "68 kg," "240 mL," "36 hours" — never a bare number.
• Check the size makes sense. Kilograms should be a smaller number than pounds; milliliters a bigger number than ounces.

❌ Common Mix-Ups

📓 Learning Journal

📝 Lesson Summary

🎉 What You've Accomplished

You can now read and write the 24-hour clock, work out when a shift ends and how long it ran, total up a week of hours, and convert between common units with a method you trust. You also added a "Time & Conversions I Can Do" page to your career-plan folder — real proof of a real skill. That's a strong step in the numeracy that healthcare work relies on every day. 🎉

❓ Common Questions at This Stage

🔭 Looking Ahead

You've handled time and conversions; next comes the money side of the work. In Lesson 3.3: Money & the Healthcare Worker, we put numeracy to work on paychecks, hours and pay, shift differentials, budgeting, and reading a pay stub — the practical money math a healthcare job involves. It builds right on the careful, check-your-work habits you practiced today.

✅ Before the Next Lesson

• Finish and save your "Time & Conversions I Can Do" page.
• Practice a few conversions in daily life — convert a clock time to 24-hour, or figure the minutes in a task.
• Write your Learning Journal entry, including how you feel about math right now.