I wanted columns that were ragged left as well as pushed up against the left. I achieved this with dummy (Z) columns of 0pt width and multicolumn headers.

However, now I can't add any space between the columns because it messes with the alignment. Even trying to add 0pt of space causes a misalignment. What is going on here?

---

MWE
===

```
\documentclass{report}
\usepackage{inputenc}
\usepackage{array}
\usepackage{booktabs}
\usepackage[singlelinecheck=false]{caption}

\newcommand{\mc}{\multicolumn} % multicolumn is too many letters...
\newcolumntype{Z}{@{}p{0pt}}   % dummy column

\begin{document}

% Value column is correctly aligned
\begin{table}[h]
\caption*{\textit{Value} column is correctly aligned}
\begin{tabular}[l]{@{} r@{ }rZ rZ @{}}
\toprule
    \mc{3}{@{}l}{Time} & \mc{2}{l@{}}{Value} \\
\midrule
            6h &  0m & &              -1.1 & \\
           19h & 15m & &              26.3 & \\
\bottomrule
\end{tabular}
\end{table}

% With \hskip, Value column is not correctly aligned
\vspace{2em}
\begin{table}[h]
\caption*{\textit{Value} column is not correctly aligned}
\begin{tabular}{@{} r@{ }rZ @{\hskip 20pt} rZ @{}}
\toprule
    \mc{3}{@{}l}{Time} & \mc{2}{l@{}}{Value} \\
\midrule
            6h &  0m & &              -1.1 & \\
           19h & 15m & &              26.3 & \\
\bottomrule
\end{tabular}
\end{table}

\end{document}

```

---

Edit: Image
===========

[![enter image description here](https://i.stack.imgur.com/v26dE.png)](https://i.stack.imgur.com/v26dE.png)

---

Edit2: Answer
=============

siunitx seems to be what I want. The following table is *way* better for what I'm trying to do.

```
\begin{tabular}[h!]{
    @{}
    S[
        table-format=2,
        table-space-text-post=\si{\hour},
        table-number-alignment=left]
    @{\hspace{5pt}}
    S[
        table-format=2,
        table-space-text-post=\si{\meter},
        table-number-alignment=left]
    S[
        table-format=-1.1,
        table-number-alignment=left]
    @{}
}
\toprule
    \mc{2}{@{}l}{Time} & {Value} \\
\midrule
     6 \si{\hour} &  0 \si{\meter} & -1.1 \\
    19 \si{\hour} & 15 \si{\meter} & 26.3 \\
\bottomrule
\end{tabular}

```

`\si{\meter}` is a bit of a hack, but I prefer `m` to `min` for minute as it takes up less space and is consistent with `d` for day and `h` for hour.

[![enter image description here](https://i.stack.imgur.com/LqweW.png)](https://i.stack.imgur.com/LqweW.png)

Thanks to everyone who replied!