{{ $birth := "2000-10-28" | time }}
{{ $today := now }}
{{ $age := sub $today.Year $birth.Year }}
{{ $monthDiff := sub $today.Month $birth.Month }}
{{ $dayDiff := sub $today.Day $birth.Day }}

{{ if (gt $monthDiff 0) }}
    {{ $age }}
{{ else if (lt $monthDiff 0) }}
    {{ sub $age 1 }}
{{ else }}
    {{ if (ge $dayDiff 0) }}
        {{ $age }}
    {{ else }}
        {{ sub $age 1 }}
    {{ end }}
{{ end }}