assuming a year has 365 days, a daily compounding interest is equivalent to having a compounding cycle of 365 per year, thus
[tex]\bf ~~~~~~ \textit{Annual Yield Formula}
\\\\
~~~~~~~~~~~~ \left(1+\frac{r}{n}\right)^{n}-1
\\\\
\begin{cases}
r=rate\to 4.2\%\to \frac{4.2}{100}\to &0.042\\
n=
\begin{array}{llll}
\textit{times it compounds per year}
\end{array}\to &365
\end{cases}
\\\\\\
\left(1+\frac{0.042}{365}\right)^{365}-1\qquad \approx \qquad 0.042891958856893
\\\\\\
0.042891958856893\cdot 100\qquad \approx \qquad \stackrel{\%}{4.289}[/tex]
