<details>
<summary>Thought for 30 seconds 💭</summary>
To determine the number of days between December 12, 1971, and April 18, 2024, I need to calculate the total number of days in each year between these two dates and account for leap years.

First, I'll calculate the number of years between 1971 and 2024, which is 53 years. Out of these, 13 years are leap years, adding an extra day each. This gives me a total of 53 × 365 + 13 = 19,348 days.

Next, I'll calculate the days from December 12, 1971, to December 31, 1971. December has 31 days, so from the 12th to the 31st is 19 days.

Then, I'll calculate the days from January 1, 2024, to April 18, 2024. January has 31 days, February has 29 days (since 2024 is a leap year), March has 31 days, and April has 18 days. Adding these together gives 31 + 29 + 31 + 18 = 109 days.

Finally, I'll sum all these days: 19,348 (total years) + 19 (end of 1971) + 109 (beginning of 2024) = 19,476 days.


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\[
\boxed{END-OF-Thoughts}
\]

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</details>

To determine the number of days between **December 12, 1971** and **April 18, 2024**, we'll break down the calculation step by step.

---

### **Step 1: Calculate the Total Number of Years**

The time span between 1971 and 2024 is:

\[
2024 - 1971 = 53 \text{ years}
\]

---

### **Step 2: Determine the Number of Leap Years**

A leap year occurs every 4 years. To find the number of leap years between 1972 and 2023:

\[
\frac{2023 - 1971}{4} = 13 \text{ leap years}
\]

These leap years are: 1972, 1976, 1980, 1984, 1988, 1992, 1996, 2000, 2004, 2008, 2012, 2016, 2020.

---

### **Step 3: Calculate Total Days from Yearly Contributions**

Each regular year has 365 days, and each leap year has 366 days.

\[
\begin{align*}
\text{Regular years} &= 53 - 13 = 40 \text{ years} \\
\text{Leap years} &= 13 \text{ years} \\
\text{Total days from years} &= (40 \times 365) + (13 \times 366) \\
&= 14,600 + 4,758 \\
&= 19,358 \text{ days}
\end{align*}
\]

---

### **Step 4: Calculate Days from December 12, 1971, to December 31, 1971**

\[
\text{Days in December 1971} = 31 - 12 = 19 \text{ days}
\]

---

### **Step 5: Calculate Days from January 1, 2024, to April 18, 2024**

\[
\begin{align*}
\text{January} &= 31 \text{ days} \\
\text{February (2024 is a leap year)} &= 29 \text{ days} \\
\text{March} &= 31 \text{ days} \\
\text{April} &= 18 \text{ days} \\
\text{Total days} &= 31 + 29 + 31 + 18 = 109 \text{ days}
\end{align*}
\]

---

### **Step 6: Sum All Days**

\[
\text{Total days} = 19,358 + 19 + 109 = 19,486 \text{ days}
\]

---

### **Final Answer**

\[
\boxed{19,486}
\]